A single-tube parallel motor controller for low cost battery electric vehicle is developed. The overall design scheme of single-tube parallel motor controller is described, and the hardware and software design schemes of the controller are introduced. A design scheme of the motor controller based on the single-tube IGBT parallel connection is proposed. The thermal simulation analysis of the vertical water-cooled radiator is carried out, and the heat dissipation effect of the single-tube parallel motor controller is studied. Finally, the bench test of the single-tube parallel motor controller prototype is carried out. The test results show that the designed controller has a good control performance.