He hailed from Xuchang 許昌 in the commandery of Yingchuan 穎川 (today in Henan) and served Liu Bei 劉備 when the latter was regional inspector (cishi 刺史) of the province of Yuzhou 豫州. Later on he joined the warlord Cao Cao 曹操 and became a trusted supporter of him in the office of palace aide to the Censor-in-chief (yushi zhongcheng 御史中丞).
Emperor Wen 魏文帝 (r. 220-226) gave him the title of Township Marquis of Changwu 昌武亭侯, and appointed him chief steward for writing (shangshu 尚書). Chen Qun submitted to the emperor a proposal to divide the posts of the officialdom in nine ranks. Posts should be occupied by persons with high potentials recommended to so-called rectifiers (zhongzheng 中正) in all provinces and commanderies. Potential candidates should be classified in nine ranks, and accordingly be chosen to fill vacancies with the same rank (see nine-rank system). Emperor Wen adopted the recommendation system, and it remained valid until the Song period 宋 (960-1279), when it was replaced by the examination system. The nine ranks of the officialdom were retained until the end of imperial age.
Chen Qun was highly rewarded and had the posts of Vice Director of the Imperial Secretariat (shangshu puye 尚書僕射), palace attendant (shizhong 侍中) and Director of the Imperial Secretariat (shangshu ling 尚書令), and was given the title of Township Marquis of Ying 穎鄉侯. He also bore the military title of General-in-chief controlling the armies (zhenjun da jiangjun 鎮軍大將軍) and was army supervisor (zhonghujun 中護軍). When Emperor Wen fell ill, he became part of a triumvirate of regents, together with Cao Zhen 曹真 and Sima Yi. His posthumous title was Marquis Jing 靖侯.