Abstract: On March 3, 2022, a massive power outage hit Taiwan, affecting 5.49 million users. In this paper, the overview of power grid in Taiwan province of China, the development process of "303" accident, comparative analysis of mainland power grid and Taiwan province power grid protectiont in "differential bus protection TA bolt logic", "line protection oscillation atresia logic" and "line protection configuration and setting" three aspects of difference, and the deficiency existing in the mainland grid relay protection improvement measures are proposed.