Xu huapin 續畫品錄 "Continued classification of painters" is a critique on painters attributed to the Tang-period 唐 (618-907) master Li Sizhen 李嗣真 (d. 696), courtesy name Chengzhou 承胄, who hailed from Zhaozhou 趙州 (modern Xiping 西平, Henan) or Huazhou 滑州 (modern Changyuan 長垣, Henan) and was palace aide to the Censor-in-chief (yushi zhongcheng 御史中丞). He was later demoted and exiled to southern China where he died.
Li Sizhen was known as an expert in music and astronomical calculation, but also for his paintings of Buddhist and Daoist deities. He had been a disciple of the painter Yin Lin 尹琳, who was also the teacher of Li Zhongchang 李仲昌 (late 7th cent.). Li Sizhen is also mentioned in the painting critique Tangchao minghua lu 唐朝名畫錄, but neither his strengths and shortcomings are described, nor is he ranked by the quality of his artworks.
Li Sizhen's abilities and works are at least mentioned in Zhang Yanyuan's 張彥遠 (815-907) Lidai minghua ji. The Xu huapin is listed in the book catalogue Junzhai dushu zhi 郡齋讀書志, but in another context. Many scholars therefore doubt that he was the author of the Xu huapin lu.
The content of Li Sizhen's book is also very similar to an earlier one written by Yao Zui 姚最 (536-602) which has the similar title Xu huapin 續畫品 or Xu huapin lu. However, Li Sizhen does not mention Yao's work in a single word. It might be that Li's book was lost at an early point of time, and later collectors tried to reconstruct it by copying sentences from Yao Zui's book.
Zhang Yanyuan's Fashu yaolu 法書要錄 lists another book by Li Sizhen, the short text Houshupin 後書品, which is a critique of 81 calligraphers that are classified in ten ranks. This book is structured in a very clear way. The lost book Xu huapin lu might thus have had a similar consistent style of composition, very unlike the received Xu huapin lu, which has a confuse arrangement.