Chinese First Quasi-Axisymmetric Stellarator (CFQS) is being constructed as an international joint project between the National Institute for Fusion Science in Japan and Southwest Jiaotong University in China. To meet the requirements of 0.1 T steady-state quasi-axisymmetric magnetic field configuration experiment, it is necessary to design and manufacture the corresponding power supply system for its magnet coil. Since the power grid capacity of the laboratory can’t achieve the power consumption required for 0.1 T operation of CFQS, the magnet coil power supply system uses 500 kVA energy storage power station, and the main circuit of the magnet coil power supply system adopts bridge thyristor rectification. In this design scheme, the line impedance is estimated according to the actual engineering situation. Considering the engineering margin, we calculate the power supply at 1.2 times of the actual load parameters, and build the Simulink simulation model of the power supply system to analyze the load current ripple and the harmonic content of the grid side. According to the simulation results, we optimize the design and reduce the output current ripple by adding a passive filter at the DC side. By this way, the output current ripple can meet the requirements of the quasi-axisymmetric magnetic field configuration.