The rectifier is widely used in rail transit, but because of the strongly nonlinear of the rectifier device makes it become one of the main harmonic source of power grid. In order to reduce the interference of harmonic current in power system, we put forward a new kind of 24-pulse commutation method to suppress harmonic wave. We analysis four aspects of this method, such as the principle of multi-pulse rectifier harmonic suppression technology, the structure and equivalent capacity of autotransformer and network side input current. DrawwingSaSconclusion that the autotransformer’s input current has good waveform and the advantage of that its equivalent capacity is far less than the output power. Finally using the electromagnetic transient simulation software PSCAD/EMTDC, we build a 24-pulse rectifier circuit simulation model of rail transit. The simulation results verify the validity of the model used in rail transit.