Abstract: The 3D magnetic-thermal-solid coupling for a small induction motor was calculated using the finite element method referencing the prototype with a skewed rotor. Firstly, the 3D-electromagnetic field of the motor on the rated load condition was calculated in consideration of the influence of the end windings. Results of the 3D electromagnetic field node loss density were coupled to the 3D temperature field model as heat sources. Then, the distribution of the temperature at different time and each point temperature changing curve versus time were obtained by exerting the boundary condition, and the aim was to simulate the transient thermal change process of the motor on the rated load condition. The internal heat transfer law was summarized from the temperature distribution at different time, and the simulation results were verified by experiments. Finally, the thermal stress distribution of the rotor cage was obtained based on the results of the rotor transient temperature field by exerting the corresponding constraints. Then the location easy to fracture was found and the cause of stress was analyzed. The calculation method used in this paper can provide a reference for the multi physical field coupling issues and lay the foundation for further research on the broken bar fault reasons and the fracture process in the squirrel-cage induction motor