The earlies record of Can Jun Shi and Can Jun in books of history was of the western conquest led by Zhang Wen (張溫) in Zhong Ping YearⅡ (中平2年) of Emperor Lin (靈帝) of Eastern Han Dynasty. Later on, the Kingdom collapsed, and was constantly ravaged by war. During Xian Emperor (獻帝) Jian An (建安) years, in Cao Cao (曹操) group, from the Prime Minister down to Generals, Governors, Magistrates, and their staff offices mostly set up the position of Can Jun Shi for consultation, and this system was not seldom seen during the age of Three Kingdoms. The origin of the Can Jun system of Wei (魏) can be ascribed to Can Jun Shi of the ending period of Eastern Han, evolving from provisionally assigned Can Jun Shi with loose and indefinite duties to be a formal position. Furthermore, the duties of Can Jun or Can Jun Shi were different according to the status and positions of their bosses. The system of Can Jun in Shu (蜀) formed during the early period of the Last Emperor when Zhu Ge Liang (諸葛亮) held the government, and it was one of the important aides of the Prime Ministry. Since Zhu Ge Liang was in charge of all the government affairs, mastering both the pen and the sword, the duty of the Prime Minister’s Can Jun was not limited to military but also interior and foreign affairs. During the late period of the Last Emperor, the Governors of the three border areas all had Can Jun, whose function was mainly to handle military affairs. Wu (吳) has not Can Jun, but we can know little about it owing to the scantiness of information.