Ji Zu Xun was a fang shi (方士) who presumably lived from the close of the Hou Han dynasty through the San Guo period. His early biographies are available in Shen Hsien Chuan (神仙傳) and Hou Han Shu (後漢書). A comparison of those two biographies reveals not a few differences. It is ascribable to the difference in attitude between one who claims the existence of a supernatural being and one who only describes historical facts. On the other hand, Han Wu Di Wai Chuan (漢武帝外傳) also contains Ji Zu Xun's biography, the content of which agrees for the most part with that in Shen Hsien Chuan. The present study is an attempt to estimate, through an inquiry into the character and the date of composition of Han Wu Di Wai Chuan and a comparison of it with Ji Zu Xun's biography in the other two works.