A new large research infrastructure for fundamental researches on the space environment, Space Environment Simulation Research Infrastructure (SESRI), is being constructed. When studying the three-dimensional magnetic reconnection of the earth’s magnetotail, the dipole coil and two magnetic mirror coils in vacuum environment are used to provide the simulated background magnetic field required for the study. To generate the amplitude and duration of the background magnetic field required by the experiment, two sets of pulsed power supplies with a total energy of 3.36 MJ are developed and tested. The pulsed power supply used to drive the dipole coil can provide a peak current of more than 9 kA when the charging voltage is not more than 20 kV, and the duration of 95% peak current is more than 5 ms, the time from peak time to 10% peak time does not exceed 130 ms; According to the experimental requirements, the pulsed power supply used to drive the magnetic mirror coil can provide a peak current of more than 8 kA when the charging voltage is not more than 20 kV, the duration of 95% peak current is more than 5 ms, and the time from peak time to 10% peak time does not exceed 130 ms. The two sets of pulsed power supplies need to work simultaneously in the three-dimensional magnetic reconnection experiment of the earth’s magnetotail.