Pre-tightening Technology of Cone Bearing: In the process of the main gear nut tightening, control the torque of the nut tightening, and detect the maximum starting torque and rotation torque of the main gear, carry out digital detection and assembly, and display the change curve of the measurement torque in real time. The double servo torque feedback system and PID control method could effectively ensure the nut tightening torque and bearing pre-tightening torque at a reasonable value and reduce the damage to the thread when the nut is tightened.