Abstract: China’s BeiDou Navigation Satellite System (BDS) construction has been completed and the system has been formally commissioned. Most of the Electric Power Systems (EPSs) for MEO satellites were developed by the Shanghai Institute of Space Power-sources. The 42 V medium-voltage fully-regulated high-power EPS has been adopted for the first time in medium Earth orbit, with an output power reaching about 3 kW. Compared with the 42 V medium-voltage semi-regulated bus power system used in the Regional Navigation BDS-2 satellite, the EPS of the BDS-3 MEO satellites has increased power by about 80%, adopting many newly developed products such as high-efficient triple junction GaAs solar cells, high-energy-density lithium ion batteries and a high-efficient autonomous power control unit (PCU). Based on the studies on the medium-voltage fully-regulated and high-power EPS technical principles, and the adaptability and reliability of various working modes, the test verifications for the EPS were conducted both on the ground and in orbit. Compared with other global navigation satellite systems such as GPS, Galileo and GLONASS, the EPS of the BDS-3 MEO satellite has a long design life time which is equivalent to that of the GPS and Galileo, but with a larger power supply capability and power ratio, distinguishing its advancement in the field of satellite power technology.