In order to improve the accuracy of the servo system at low temperature, the mechanism that the load torque of the telescope increase along with the temperature decrease must be deeply understood. Firstly, the influence factors of friction torque of bearing and the influence of low temperature on load torque were analyzed. The lubricant viscosity with temperature variation was studied. The relationship between load torque and grease was tested and discussed. The results indicate that the fluctuation of load torque without the grease at low temperature is decreased and the linearity of load torque is increased. The influence of clearance on bearing friction torque was also analyzed. The expansion coefficient of different materials at different temperatures was measured by resistance strain gauge method. The correlation coefficient between torque and material expansion was established. The result indicates that the load torque at low temperature is 6.67 times load torque at normal temperature, and the maximum of shortening of material reaches 960 με. The research on the mechanism of cryogenic load torque in this paper can provide theoretical and experimental data for the precise control of the telescope under extreme environment.