The permanent magnet motor for electric submersible pump works in a special environment of high temperature and high pressure. The lubricating oil is used as the lubricating and cooling material of the submersible motor and lubricating oil moves with the rotor in the air gap. In previous studies, only the oil friction loss of the rotor is considered. However, compared with cooling methods such as air cooling and water cooling, the higher viscosity of the lubricating oil is a factor that cannot be ignored when oil cooling. And the motor speed of the electric submersible pump is high. Whether the oil friction loss caused by lubricating oil on the stator side can be ignored and its influence on the temperature rise of the motor need to be further explored. Therefore, taking a 15 kW submersible permanent magnet motor as an example, the approximate analytical formula of the stator oil friction loss is derived, and the relationship between the stator oil friction loss and the rotor oil friction loss is proposed. Based on computational fluid dynamics and fluid-structure coupling heat transfer theory, the fluid flow characteristics at the air gap are studied. The accuracy of the approximate analytical formula for stator oil friction loss is proved. The temperature rise distribution of each part of the motor is obtained, and the influence of the stator oil friction loss on the temperature rise of the motor is analyzed.