In order to adapt to the development trend of high speed, high pressure and large flow of three screw pump, it is the key to strictly control the screw deformation and its related clearance to reduce the leakage in the pump. The temperature field in a three screw pump was applied as a load on the surface of the driving and driven screws, and the temperature structure coupling numerical simulation analysis was carried out. The deformation law of the driving and driven screws caused by the temperature and working torque in the three screw pump under different working conditions was studied, and the deformation and stress changes of the driving and driven screws under the action of each individual physical field and coupling were compared. The results show that the thermal deformation of the driving and driven screws is more obvious than that of the torque. With the increase of the working temperature, the thermal deformation of the driving and driven screws increases, and the thermal stress produced by the driving and driven screws is proportional to the working temperature. Under the same working temperature, the deformation of the driving and driven screws increases in the X, Y, Z directions, while the deformation in the Z direction is far greater than that in the X direction and Y direction.