The invention discloses an electric auxiliary single-stage turbocharging system for a fuel cell. The electric auxiliary single-stage turbocharging system comprises a compressor for providing the fuelcell with clean compressed air, a turbine for recovering energy and a drive motor, wherein the compressor, the turbine and the drive motor are coaxially connected; the turbine and the compressor are arranged at two ends of a rotating shaft of the motor separately; a radial flow/mixed flow centrifugal compressor is adopted as the compressor; the turbine is a radial flow turbine expander; and the motor is a permanent magnet synchronous motor. The electric auxiliary single-stage turbocharging system for the fuel cell can meet the requirements of a high-power fuel cell power system and cover the full working range of the fuel cell power system, and the electric auxiliary single-stage turbocharging system is compact in overall structure and high in efficiency.