Abstract: To address the problem of temperature rise due to losses in large wet submersible induction motors, the basic core losses, no-load core additional losses, and load core additional losses, winding basic losses, winding additional losses, and winding end losses that exist during the operation of large wet submersible motors are analysed. In view of the slow speed of the finite element fluid-solid coupling simulation of the temperature field, a temperature rise calculation program for large wet submersible induction motors is developed based on the basic law of heat transfer, using an optimised equivalent heat path diagram, and based on the equivalent heat path method. The calculation programme is able to calculate the temperature rise of large submersible induction motors efficiently and accurately. Finally, the time-harmonic field finite element modelling and analysis of a 160 kW large-scale wet submersible motor is carried out to obtain the graphs of each loss in the core, stator copper consumption, rotor copper consumption and the rate of rotation of the motor, and the temperature rise of the motor is calculated by the temperature rise calculation software, which is compared with the prototype experimental test to validate the accuracy of the optimized equivalent thermal circuit diagram.