He came from Weijun 魏郡 and studied the Confucian Classic Yijing 易經 "Book of Songs" under the Confucian scholars Meng Xi 孟喜 and Han Ying 韓嬰. Nominated as a "classicist" (mingjing 明經), he was appointed court gentleman (lang 郎).
During the reign of Emperor Xuan 漢宣帝 (r. 74-49 BCE) he was classified as "straightforward and upright" (fangzheng 方正), which allowed him to be appointed to the post of Grand master of remonstrance (jian dafu 諫大夫), then supervisor of gate gentlemen-attendants (langzhong hujiang 郎中戶將) and finally metropolitan commandant (sili xiaowei 司隸校尉).
Gai Kuanrao was a honest, upright and incorruptible official that was feared by many influential persons at the court. Only when he contradicted the emperor in an affair concerning the influence of the eunuchs on the Palace Secretariat (zhongshusheng 中書省) he was put into prison, where he committed suicide.