Abstract: There were mismatches between the big population in Yongchang and its remote location recorded in JunGuoZhi. History of the Later Han Dynasty by Sima Biao in 140, which was questioned by many scholars. The amount population at that time, however, was reliable if the special growth of ethnic groups population and the ordinary growth of Chinese population were understood in different ways. Considering the prosperity of the Southern Silk Road and the development of Yongchang county at that time , we may find that the population recorded in JunGuoZhi. History of the Later Han Dynasty by Sima Biao is realizable and reasonable. Therefore, the specialty in the special period should be taken into account when the population of ethnic groups is estimated.

Key words: JunGuoZhi. History of the Later Han Dynasty, Yongchang County, Ailao People, population ethnicgroup, Southwestern Silk Road