In order to prevent the wives and relatives doing government. Tuo Bagui formulated the system of killing mothers of crownprinces.This system had heen strictly implemented before Emperor Xiaowen. Nevertheless, the phenomenon of imperial government hy empresses was still frequent, especially in the early Northern Wei Dynasty, these two presented as a parallel development. This phenomenon * 8 appearing was because of the defects of the system and the advantage of the imperial government hj empresses.