Two permanent magnet synchronous motors (PMSM) whose rotor magnetic circuit structures were radial and tangential were designed. vector potential and energy methods were used to calculate the electromagnetic parameters of the motors. Based on the mathematical model, the torque characteristics were calculated, control performances within constant torque and constant power control area were analysed and the corresponding control methods were given. Simulation results showed that dynamic performance and overload capacity of the radial structure were better while the flux-weakening speed expansion capacity of the tangential structure was better, which were consistent with the theoretical analysis. The final conclusions provided some reference for the design of the two kinds of PMSM.