He hailed from Xincheng 稚卿 in the commandery of Zhuojun 涿郡 (close to modern Xushui 徐水, Hebei). During the reign of Emperor An 漢安帝 (r. 106-125 CE) he was made palace attendant (zhonghuangmen 中黃門), then chief steward (jishi 給事) of the Changle Palace 長樂宮. When the Emperor died, he conspired with Wang Kang 王康 and other eunuchs and brought the Prince of Jiyin 濟陰 to the throne, Emperor Shun 漢順帝 (r. 125-144), and managed the assassination of Yan Xian 閻顯, the most influential male relative of Empress Dowager Yan 閻太后. He was therefore bestowed the title of Marquis of Fuyang 浮陽侯 and given the post of commandant of cavalry (jiduwei 騎都尉).
Because of an affair he resigned from his post and was given the title of Marquis of Yicheng 宜城侯. In 132 he was granted the title of Commandant-in-chief of the chariots (fengche duwei 奉車都尉), but died soon and was buried with the honours of a horse-and-chariot general (cheji jiangjun 車騎將軍). His posthumous title was Marquis Gang 宜城剛侯.
Sun Cheng was succeeded by his adoptive son Sun Shouxi 孫壽襲, which was the first occurrence that an ennobled eunuch passed on his title to an adoptive son.