During the rated operation of canned motor for vacuum dry pump, insulation aging may occur when the temperature rise is too high, which threatens the operation safety of the vacuum dry pump. Aiming at this problem, the water-cooled structure of a 4.5 kW canned motor for vacuum dry pump is designed, and the temperature field simulation analysis and experiment are carried out. A three-dimensional model of the canned motor is established by using mechanical software, and a simulation model for calculating the temperature field of the canned motor is established by using finite element analysis software. By setting the thermal source and boundary conditions, the temperature field distribution in each part of the motor is obtained. An experimental platform is set up to carry put the temperature rise test, and the characteristic curves of temperature changing with time are obtained during the start process in cold condition to stable process after temperature rise. Combined with the temperature field analysis and experimental results, it showes that the internal temperature of the motor meets the thermal design requirements. This research has a certain guiding significance for the subsequent investigation of temperature field and the design of cooling system of the canned motor for vacuum dry pump.