Background: The motor cooling system is mainly used in aerospace, automotive, and marine fields, where the motor system is cooled to extend the service life and safety of the motor. The running power of motors rises too fast, which leads to the failure of heat dissipation as expected and shortens the service life of motors. Therefore, it is necessary to choose an appropriate cooling mode for motors to improve their cooling structure, reduce their temperature rise, and improve their reliability and service life. The internal motor cooling system can perform fixed-point heat dissipation, but the overall heat dissipation is poor. The external motor cooling system can perform overall heat dissipation but has high requirements on the structure. Over the years, the application and development of motor cooling systems have gained more and more attention. Objective: This paper discusses the structural characteristics, advantages, and development trends of the motor cooling system in order to reduce the temperature rise of the motor and improve its reliability and service life. This paper aims to provide an overview and systematic guidance for future designs of the motor cooling system. Methods: According to the structural characteristics of the motor cooling system and the requirements of the motor application field, the most typical internal cooling system and external cooling system in the motor cooling system are summarized. Results: By analyzing the causes and hazards of motor heating, the limited requirements of the motor system in use are summarized. The motor system is classified and compared based on the structure, heat dissipation principle, and use of the motor heat dissipation system. The characteristics of small volume and strong heat dissipation ability are also summarized. Based on the analysis of the internal and external cooling system, the problems of complex structure and poor cooling effect are summarized, and the future development trend and direction of the motor cooling system are discussed in detail. Conclusion: This paper divides the motor cooling system into an internal cooling system and an external cooling system according to the specifications and operating environment. This paper expounds on internal and external cooling systems' different principles, advantages, and disadvantages. This paper summarizes the cooling systems in recent years in order to facilitate their subsequent development and use. The main components of additional patents for future inventions are motor cooling systems, innovation in structure simplification, and cost performance optimization.