After Li Yuan established the Tang dynasty as its Emperor Gaozu, he created Lu Chisong the Duke of Fanyang.
Emperor Taizong was impressed by the clarity of his report, and promoted him to be a low-level official at the ministry of civil service.
Lu was demoted to be the secretary general to the commandant at Yi Prefecture (益州, roughly modern Chengdu, Sichuan).
As of 659, Lu was serving as the minister of treasury, when he was given the designation Canzhi Zhengshi (參知政事), making him a chancellor de facto.
Later that year, when the former chancellor and Emperor Gaozong's uncle Zhangsun Wuji, who had already been exiled on suspicion of treason, was accused of further plotting, Lu, along with fellow chancellors Li Ji, Xu Jingzong, Xin Maojiang, and Ren Yaxiang were put in charge of the investigation (although it was Xu, who was an ally of Emperor Gaozong's powerful wife Empress Wu (later known as Wu Zetian), who drove the investigation), which resulted in Zhangsun's forced suicide.
However, in 660, he was accused of mishandling the ministry of treasury, and he was removed from his offices, and further was sent to Run Prefecture (潤州, roughly modern Zhenjiang, Jiangsu) to be its prefect.
He was subsequently made the secretary general of Yong Prefecture and given the honorific title Yinqing Guanglu Daifu (銀青光祿大夫).
He soon requested retirement on account of old age, and Emperor Gaozong agreed, further giving him the honorific title of Jinzi Guanglu Daifu (金紫光祿大夫).