A 30kW permanent magnet synchronous motor for electric vehicle is designed and field-circuit coupled method are used to improve the accuracy of the design. Structure optimization includes rotor and cooling structure optimization, meanwhile many physical fields are caculated to verify the rationality of structure design, and important motor parameters are obtained by magnetic field calculation. The performance of constant torque and constant power are analyzed. Regional performance, peak capability and flux-weakening level are obtained to match with start, acceleration, top speed and other properties of electric vehicle. The study on key technologies of motor design is aim at meeting the requirements of motor design for electric vehicle.