When switching between multiple power systems, the performance of the uninterruptible power system (UPS) is greatly affected due to the different grounding modes of the neutral wire. Firstly, based on the equivalent model of multi-power system circuit, the advantages and disadvantages of different circuit structures are discussed, and the performance index of multi-power system circuit is simulated and verified by building MATLAB/Simulink simulation model；Based on the circuit of the multi-power system, the MATLAB/Simulink simulation model of the UPS circuit of the multi-power system is built, and the key performance indexes of the UPS circuit of the multi-power system are simulated. Secondly, three kinds of UPS circuit structure optimization schemes of multi-power system are proposed to optimize the performance indexes of UPS circuit of multi-power system, such as no stray current, no neutral line shunting, continuous neutral line grounding reference, electrical isolation between multiple input power sources, input power and output power sources, and input power and bypass power sources. Finally, three optimized and enhanced circuit MATLAB / Simulink simulation models were constructed, and the performance indexes of the three UPS circuits were simulated. The experimental results demonstrate that the improved scheme three "multi-power system UPS power circuit with bypass isolation transformer" has the optimal performance indexes of the multi-power system UPS power circuit.