Among the refugee commanders of his time, he was one of the very few to be trusted by the imperial court, and by the end of his life, he formed part of a triumvirate within the Jin government that consisted of him and two other top-ranking ministers, Yu Liang and Wang Dao.
When Sima Lun usurped the throne in 301, Xi Jian refused to return to his service despite offers of lofty titles.
The same year, Sima Lun was killed, and Xi Jian returned to the government to serve Liu Shi (劉寔).
After Chen Wu was defeated, Xi Jian returned to his hometown in Gaoping, where most of the inhabitants were desperate to escape the ongoing war in the north.
Sima Rui grew ill from the defeat and died the following year, leaving the throne to his son, Emperor Ming of Jin.
Emperor Ming wanted someone to challenge Wang Dun within the state, so he made Xi Jian the Inspector of Yanzhou and Chief Controller of north of the Yangzi.
Wang Dun criticized the minister Yue Guang for his lack of talent while praising his counterpart Man Fen (滿奮).
Xi Jian turned down the appointments Emperor Ming gave to him and instead advised him to reach out to Su Jun and Liu Xia (劉遐) to join his war against Wang Dun.
Xi Jian told Emperor Ming that Wang Dun's remains should be given back to his family members to display himself as righteous.
[7] Later, Xi Jian called for Emperor Ming to execute Wang Dun's partisans on two occasions, but both times he found his suggestions rejected.
The capital was lost to rebel forces the following year and Su Jun became the de facto head of state with Emperor Cheng of Jin under his control.
[9] Yu Liang slipped away to Xunyang (尋陽, in present-day Huangmei County, Hubei) where he met Wen Jiao and conspired with him to reclaim the capital.
Xi Jian provided the final blow to the rebellion as he sent his general Li Hong (李閎) to destroy Han Huang and the remaining rebels at Mount Pingling (平陵山, in present-day Liyang, Jiangsu).
[12] For his efforts, Xi Jian was made Palace Attendant, Minister of Works, and Duke of Nanchang County by Emperor Cheng.
In the beginning of 331, Xi Jian repelled a Later Zhao invasion in Lou County (婁縣; in present-day Kunshan, Jiangsu) led by Liu Zheng.