Electric actuators with fast dynamic response and high torque density are widely used in aerospace and industrial applications. In this paper, the design and optimization of a short-term high-overload permanent magnet synchronous motor (STHO-PMSM) is presented. The rated working point is optimized according to the operating conditions of the motor. The effect of electromagnetic load on the extreme torque which mainly include ampoule number and the magnetic energy of the PM is researched. Due to the nonlinear saturation influence, the equivalent magnetic network model is established. The saturation torque discount factor is proposed to quantify the degree of the core magnetic saturation. Winding temperature model is presented to inspect the motor reliability. To verify the feasibility and accuracy of mathematical model analysis (MMA), the performance of the motor in different currents is investigated compared to the finite element analysis (FEA). A prototype motor is manufactured and tested. The results of the MMA, FEA, and experiment show that the designed motor can achieve the high performance with the 10 times overload in a short time. The method of the MMA can relatively accurately predict as well as take less time consumption.