In order to accurately study the temperature field distribution of the submersible motor, the author proposes the numerical sensing and simulation analysis of the three‐dimensional flow field and temperature field of the submersible motor. For a marine air gap water‐cooled internal submersible permanent magnet motor, based on the principle of computational fluid dynamics (CFD), numerical simulation analysis and geometric structure improvement of the three‐dimensional flow field and temperature field of the motor were carried out, eliminate the reverse flow phenomenon in the internal flow field of the motor, improve the heat dissipation efficiency of the whole machine, and optimize the flow field and temperature rise of the motor. Experimental results show that after the motor geometry is optimized, the flow rate of the cooling water in the air gap channel is 36.7 L/min, which is 7.9 L/min higher than the original model, it means that the heat in the motor can be better carried away by the water flow in the air gap channel. It is proved that the results obtained in this study have certain reference significance for the geometric structure design of the submersible motor.