In this paper, the development trend of time synchronization system in the power system was analyzed, and a new Beidou II/GPS dual-mode satellite navigation receiving module was introduced developed, which leads to the development of a dual-mode synchronization clock for power system. The receiving module supports not only independent work mode of Beidou or GPS, but also unite work mode of Beidou and GPS. It has great strategic significance for the safety and stable of power system. The Time synchronization clock has multi output information format including RS232/485, inter-range instrumentation group-B（IRIG-B）, pulse and network time protocol（NTP）/precision time protocol（PTP）, which can be a precise time source for kinds of automation devices in the power system.