He hailed from Chang'an 長安 (modern Xi'an 西安, Shaanxi) and was the son of a commandant of the guard. Gu Yong started studying the Confucian Classics at an early age and was recommended for appointment by Censor-in-chief (yushi dafu 御史大夫) Fan Yanshou 繁延壽, so that he was made aide of the Chamberlain for Ceremonials (taichang cheng 太常丞).
During the reign of Emperor Cheng 漢成帝 (r. 33-7 BCE) Gu Yong attracted the protection of the powerful regent Wang Feng 王鳳 and rose to the office of Grand master of splendid happiness (guanglu dafu 光祿大夫). He was soon appointed governor (taishou 太守) of the commandery of Anding 安定, then regional inspector (cishi 刺史) of Liangzhou 涼州 and then returned to the court as Senior grand master of the palace (taizhong dafu 太中大夫).
Emperor Cheng was at that time open for consulation from smaller officials and accepted suggestions by Gu Yong for a better government. In 12 BCE he was made governor of Beidi 北地 but a year later was allowed to return to the capital as Chamberlain for the National Treasury (dasinong 大司農), after being recommended by general Wang Gen 王根. Yet Gu Yong soon asked to retire because of illness.
As a scholar, Gu Yong was very interested in the administrative classic Zhouguanli 周官禮 and the interpretation of natural disasters as a Celestial response to bad government, as explained in Jing Fang's 京房 interpretation of the Yijing 易京 "Book of Changes", Jingshi yi 京氏易. Somewhat more than 20 memorials written by Gu Yong have survived.