Compared with the traditional single-point measurements, multi-point synchronous magnetic field measurements can give more accurate space current density because multi-point measurement can eliminate the temporal change in the magnetic field. Based on the current density inversion method for multi-point magnetic field measurements, the inverse current density and its error is simulated, and the effects of some factors, on the space current density inversion are analyzed. These factors conclude the number of satellites, satellite formation configuration, satellite positioning precision, satellite attitude determination error, magnetic field measurement accuracy, external magnetic field intensity, and external current density and so on. Simulation results show that 5-point measurements are better than 4-point measurements, and satellite attitude determination error, satellite formation configuration and external magnetic field intensity are main factors causing the error of current density. According to the simulation, the maximum error of current density near the equator is about 24% as the attitude determination error is 0.001° and the satellite formation scale is about 100km.