″San Kung″was one of the official positions which existed for the longest time in the history of ancient Chinese civil service system . The historical transitions make it hard to grasp the manifold connotations of the name , leading to constant misinterpretations . This paper divides the history of ancient China into six periods : (1) the Pre-Qin period;(2) the Qin- Han period;(3) the Two Jin periods and the Southern and Northern Dynasties;(4) the period between the Sui and Tang Dynasties to the early Song Dynasty;(5) the Huizong period of the Southern Song Dynasty;and (6) the period from late Qinzong of the Song Dynasty till the Yuan , Ming , and Qing Dynasties . By tracing the source and development of″San Kung″, the paper examines its transition from an alternative name for the prime minister into an official rank .