He was considered to be a capable and diligent ruler, who at one point militarily expanded at the expense of the Northern Qi.

Chen Daotan died in 548 or 549, while commanding the guards in resisting a siege of the palace at the capital Jiankang by the rebel general Hou Jing.

As part of this alignment, Chen Baxian was given the post of defending Jingkou (京口, in modern Zhenjiang, Jiangsu).

(Chen Xu had previously married a wife, Lady Qian, while he was at his home commandery of Yixing (義興, roughly modern Huzhou, Zhejiang), but Lady Qian did not accompany him to Jiangling) In 554, rival Western Wei attacked Jiangling and captured it, executing Emperor Yuan around the new year 555.

(Chen Xu also welcomed his first wife Lady Qian to his mansion, but as Princess Liu was of an honored birth as the daughter of a Liang princess, she retained the position of his wife, although she gave due respect to Lady Qian) Chen Xu quickly became one of his brother Emperor Wen's key subordinates.

In spring 566, Emperor Wen was seriously ill, and Chen Xu, along with the other key officials Dao Zhongju (到仲舉), Kong Huan (孔奐), Yuan Shu (袁樞), and Liu Shizhi (劉師之), attended to him.

When Chen Xu considered doing so, his associate Mao Xi (毛喜) and the general Wu Mingche persuaded him that he needed to remain in the palace.

Once Mao confirmed so, Chen Xu arrested Liu and ordered him to commit suicide, while demoting Dao to a lesser position.

Emperor Fei's brother Chen Bomao (陳伯茂) the Prince of Shixing, whom Chen Xu believed to have participated in both Liu's and Dao and Han's plots, was stripped of his governmental posts and ordered to keep Emperor Fei company.

Wu and Chunyu were able to ram Hua's, Northern Zhou's, and Western Liang's fleets, causing them to collapse.

He created his wife Princess Liu empress and his heir apparent Chen Shubao crown emperor.

Emperor Wen's sons continued to have honored positions as imperial princes and held key posts, but none had particularly high power.

In spring 573, Emperor Xuan resolved to attack Northern Qi—but when he discussed the matter with his officials and generals, they had split of opinion.

By fall 573, Wu put the important city Shouyang (壽陽, in modern Lu'an, Anhui) under siege, and he captured Shouyang in 573, capturing and killing the Northern Qi general in charge of defending the city, the former Liang general Wang Lin.

In spring 578, the Northern Zhou general Wang Gui (王軌) thoroughly crushed Wu, capturing him.

With the people's hearts shaken by the great defeat, in fall 578, Emperor Xuan held a ceremony in which the officials reaffirmed their loyalty to the state.

In summer 580, Northern Zhou's Emperor Xuan died suddenly, and his father-in-law Yang Jian seized power as regent.

Emperor Xuan sent the generals Fan Yi (樊毅), Ren Zhong (任忠), and Chen Huiji (陳慧紀) to attack Northern Zhou's southern provinces to aid Sima, whom he created the Duke of Sui.