A geomagnetic dynamic simulator was designed, and attitude simulation application method was proposed. Three pairs of square Helmholtz coil system was designed, and the geomagnetic field was cancelled by DC current, forming a zero magnetic field space and generating controlled size and direction magnetic field. Three DC current sources were adopted to produce the current for canceling geomagnetic field and the desired magnetic field. The geomagnetic field was offset without three DC power, the premise of saving cost and ensure the accuracy. As the magnetometer accuracy and dynamic capability does not take into account two indicators, so calibration mode, select high-precision magnetometer, or for remanence measurements. The selection of simulation in the dynamic simulation using magnetometers can meet the small satellite in orbit simulation requirements.