The promotion of official rank was a matter of great concern to the ancient bureaucrats under the Taiho Codes (701), since all prerogatives, social and economic, were conferred upon the bureacrats according to their official ranks. Therefore, the system of evaluation of their duties, on which the promotion of rank was based, is worth studying.There existed four ranks in the evaluation in accordance with the kind and class of official duty or position in the administrative mechanism. The annual standard and method of evaluation were adopted on the assumption of a definite number of days of duty. The consolidated results in the course of a certain period of years in respective classes decided the suitability of official rank and degree of promotion.The characteristics are shown as follows:1. The method of evaluation of duty, though complicated, has a system based upon consistent principles.2. The annual evaluation, consolidated in a certain period of years, is directly linked with promotion.3. This method of evaluation of ancient bureaucracy, especially by the aristocracy, which had different standards according to the official rank and position is worth noticing, since it became a factor in producing cliques among the aristocracy.