Based on the dynamics theory of rolling bearings, the fluid-solid-thermal three-phase coupled numerical analysis method is used to study the temperature field and strength of the cage in the ultra-low temperature environment. The influence of the temperature distribution, stress distribution and inlet flow rate of the cage on the fluid flow rate and fluid pressure is obtained. The results show that the temperature of the cage decreases with the increase of the inlet flow rate and the maximum temperature is at the circumferential position of the pocket; the cage stress increases with the increase of the inlet flow rate and the maximum stress is at the axial position of the pocket.Research can provide reference for solving bearing life extension and reliability problems in ultra-low temperature environment