Transport commissioners (zhuanyunshi 轉運使) were high officials responsible for the transport (see grain transport, caoyun 漕運) of tribute grain (caoliang 漕糧) to the Imperial Granary (taicang 太倉) in the capital Chang'an 長安 (modern Xi'an 西安, Shaanxi). The office was introduced during the Tang period 唐 (618-907) and experienced considerable changes in the range of duties until the Song period 宋 (960-1279).
During the first half of the Tang period, officials were ad hoc made responsible for transport, yet from 713 on it became a regular office. At that time Li Jie 李杰, prefect of Shaanzhou 陜州, was appointed water-and-land transport commissioner (shuilu fayun shi 水陸發運使), and organized the transport of grain from the region around Luoyang 洛陽 to the west. The duty was often taken over by the metropolitan magistrate (yin 尹) of Henan 河南 (i.e. Luoyang), but this type of transport was given up in 811.
In 723 Pei Yaoqing 裴耀卿 (681-744) was the first transport commissioner of Jianghuai 江淮. He managed the transport of grain from the region of River Huai and the lower Yangtze region to Chang'an. He built a row of transshipment granaries along the whole route and so introduced a new system by which the grain was not brought by a flotilla of boats from the place of origin to the capital, but in a relay system in which the grain was reloaded in each station. By this method, it was easier to adapt to the conditions of each river system by using boat types more suitable to the local requirements. The new method also helped to increase the velocity of transport, as the relay system helped avoiding delays. Between the Three Gorges 三門峽 of the Yellow River and Chang'an, Pei Yaoqing had a better road built, also with granaries along the route, and so accelerated the overland transport.
The office of transport commissioner became even more important after the rebellion of An Lushan 安祿山, when northern China was devastated by war and an increasing number of military commissioners (fanzhen 藩鎮) refused to hand over taxes to the central government. The treasury of the Tang dynasty almost exclusively relied on the income from the trade monopoly of salt in the Jiang-Huai region. During the reign of Emperor Daizong 唐代宗 (r. 762-779), Liu Yan 劉晏 (718?—780) was salt and transport commissioner, and change the old system once created by Pei Yaoqing. The salt revenue was used for financing the grain transport system, and he recruited labourers entrusted with the transport. The boat types were again more adapted to the local conditions, and the system refined.
Based on these measures, the annual transport volume of 1.11 million shi 石 "bushels" (see weights and measures) gradually rose. From then on, the two offices of salt-and-iron commissioner (yantieshi 鹽鐵使) and transport commissioner were unified to salt monopoly and transport commissioner (yantie zhuanyun shi 鹽鐵轉運使). New background offices were created as capital liaison representations (liuhouyuan 留後院) in Yangzhou 揚州 and Jiangling 江陵 (i.e. Nanjing), from where vice transport commissioners (yantie zhuanyun fushi 鹽鐵轉運副使) oversaw the fresh supplies and controlled the salt revenue.
From 810 on the representation in Jiangling also took over the collection of tax revenues south of the rivers Jing 荊, Heng 衡, Han 漢 and Mian 沔 , and that of Yangzhou that south of the Yangtze and the Huai River, as two-tax comissioners (liangshui shi 兩稅使, see two-tax system). The administrative responsibilities of the transport commission was thus even extended to that of taxation. Moreover, the officials of the representations were given the title of Censor (yushi 御史), with the right to inspect and control local officials, and in 850 Wei Mo 魏謩 (793-858) suggested to extend their rights even to jurisdictional matters. Transport commissioners thus transformed from specialized officials to general administrators.
In several cases the transport commissioners were even endowed with the title of Counsellor-in-chief (zaixiang 宰相). The office was more often taken over by high officials of the central government, and occasionally also by the surveillance commissioner (guanchashi 觀察使) of Zhexi 浙西 or the military commissioner (jiedushi 節度使) of Huainan 淮. If the official was residing in Yangzhou, he had a deputies in Chang'an, called capital representations (shangdu liuhou 上都留後). On some occasions the regions in questions were divided into two parts, and controlled by two persons in charge. In 766, for instance, Liu Yan was commissioner of Dongji 東畿, Huainan 淮南, Zhejiang 浙江, and Shannan-Dong 山南東 (the eastern part of the empire), while Diwu Qi 第五琦 (712-782) was commissioner of Jingji 京畿, Guannei 關內, Hedong 河東, Jiannan 劍南 and Shannan-Xi 山南西 (the western part), and in 782, Bao Ji 包佶 (d. 792) was commissioner of Biandong 汴東, Cui Zong 崔縱 of Bianxi 汴西. Yet normally, a commissioner was either responsible for the whole empire, or only a certain part of it, like Wei Shaoyou 魏少游 (d. 771), who was transport commissioner of Shuofang 朔方.
In the early Song period transport commissioners were used in temporary offices (suijun zhuanyunshi 隨軍轉運使) to collect funds for military finance. Emperor Taizong 宋太宗 (r. 976-997) planned to use transport commissioners to diminish the power of the military commissioners, and in each circuit (lu 路) one was appointed. The office was called transport commission (zhuanyunshi si 轉運使司), or short grain transport office (caosi 漕司). They were responsible for collecting taxes, censoring the officialdom, caring for peace and order, carrying out legislation, and recommending talented persons for official positions. Transport commissioners were in fact nothing else than general administrators of territorial units. Only after 1007 Emperor Zhenzong 宋真宗 (r. 997-1022) created the offices of the superintendency of penal affairs (tidian xingyu si 提點刑獄司) and the pacification commission (anfusi 安撫司), who took away the respective duties from the transport commissioners. For those of official rank 5 or higher, or those supervising the revenue collection of more than one circuit, a special title was used, namely transport commissioner-in-chief (du zhuanyunshi 都轉運使).
The "barbarian" dynasties in northern China, the Liao 遼 (907-1125), Western Xia 西夏 (1038-1227) and Jin 金 (1115-1234), followed this system and likewise used the office of transport commissioner (then called caoyunsi 漕運司) to administer grain transport and tax revenues. In 1262 Ahmad Fanākatī (A-ha-ma 阿合馬, d. 1282) was appointed chief organizer of the grain transport of all circuits of the Yuan empire 元 (1279-1368), which means that he was responsible for all tax revenues. In all circuits throughout the empire, transport commissioners were appointed to collect taxes. Soon thereafter supervisorates-in-chief (zongguanfu 總管府) were created that took over tax collection in all circuits. Yet in 1275 eleven new transport commissions were created to increase the tax revenue, particularly in regions of salt production. The officials appointed for this duty were called yanyunshi 鹽運使 or zhuanyanyunshi 轉鹽運使.
During the Ming 明 (1368-1644) and Qing 清 (1644-1911) periods the office of transport commissioner was exlusively used to administer the salt revenue, while the transport of tribute grain along the Grand Canal was administered by the Director-general of grain transport (caoyun zongdu 漕運總督).