Abstract: A high reliable dual power switching device with isolation function applied to the safety level circuit power supply of nuclear power plants is designed, and the device architecture, hardware parameter calculation, control algorithm, and software design process are introduced. The device adopts a parallel configuration of main power supply module and standby module, where each module is an isolated phase-shifted full-bridge circuit, enabling uninterrupted parallel power supply. In order to meet the requirements of IEC and NB/T nuclear power safety standards, the Texas Instruments TMS570LS1227 industrial grade safety chip are used by the device and the control software complies with the IEC 60880 safety standard. A 2×4.4 kW prototype is built. The dual power switching and short circuit experiments have verified that the dual power switching device can fully meet the requirements of uninterrupted power supply for safety level circuits.