With the development of all-electric technology, electric servos have been widely used in aerospace and military applications. The rudder system motor requires high power density, high dynamic response and high reliability. Permanent magnet synchronous motors are widely used in servo systems for servos due to their simple structure, high torque density, high power density, and high efficiency. High power density motors generally refer to high speed and high power density motors and high torque and high power density motors. For the servo system, it is mainly a high torque density motor, which can meet the high dynamic response performance during frequent acceleration. There are many researches on high torque density motors at home and abroad, with various structures, such as high temperature superconducting machines, slotless cylindrical linear motors, transverse flux motors, and switched reluctance motors. Although the power density of this type of motor is high, its technological development is still not mature enough and its reliability cannot be guaranteed. This paper mainly uses rotating surface-mounted permanent magnet synchronous motors. Short-time high overload motor refers to the ability to output a momentary large overload in a short-time state at a constant speed of the motor to complete the predetermined action of the actuator. In recent years, the research on short-time high overload motors has been increasing. Domestic Harbin Institute of Technology and Tianjin University have done a lot of work. There are more researches on the thermal aspects of short-time cycle motors in foreign countries. In summary, scholars at home and abroad focus on high power density and temperature field analysis of short-term high overload motors, and lack of analysis and research on how to improve the motor's ultimate torque output capacity and the impact of the external environment on short-term high overload motors. Based on the actual engineering background, this paper analyzes the influence of electromagnetic load on the motor's overload capacity. By analyzing the effect of the number of ampere turns on the limit torque of the permanent magnet synchronous motor, the number of series windings of each phase of the motor is optimized; the effect of the overload multiple on the loss distribution of the motor is analyzed; and the motor is analyzed in different environments by the finite element method Temperature rise rule under long-time operating system, short-cycle operating system and short-time high overload conditions under temperature; the correctness of theoretical analysis is verified by experiments.