Abstract: A simulator which can provide a dynamic geomagnetic environment for spacecraft on MEO/LEO is introduced, and its system make-up, the structure of the coil, parameters of the magnetometer and power supply, controlling and debugging methods are discussed. The magnetic fields on orbit are calculated according to WMM2000 geomagnetic field model, and the expression for magnetic and current is obtained with numerical analysis. The geomagnetic field on MEO/LEO is simulated dynamically using the programmed power supply.