Maintenance and servicing to the EMU, in order to guarantee the operation safety, often need to stop high voltage power supply, using the ground power supply. As a result, need to provide a safe, stable and reliable ground auxiliary power supply for the EMU, ensure the normal maintenance, servicing and operation of various types of EMU. To this end, this paper based on the deployment of the ministry of railways and the requirements for configuration of ground power supply to the EMU, Analyze requirements of the auxiliary power supply system to the CRH2 EMU, on this basis, design the auxiliary power supply and its control system.