Abstract: Based on a close research on historical literatures，this paper studies the family background and life story of Cai Yong，an accomplished scholar in East Han Dynasty.Cai Yong′s life happened to be at the turning point of the East Han Dynasty from a downfall to complete collapse.A versatile scholar rarely found in Chinese history，Cai was highly accomplished and had profound and far reaching influences.The author，probing into the social and political reasons for his frustrating life experience，concludes that Cai′s life falls into the following 5 stages：adolescence well known for his talents，retirement in the countryside，official career in the middle age，fugitive life in the southeast of China，surrender to Dong Zhuo′s force and death in jail.

Key words: Han Dynasty, Cai Yong, family background, life story, Dong Zhuo, Wang Yun, Hu Guang