The main function of the automobile transmission shaft is to support the rotating body and transmit power. The working conditions are generally subject to alternating torque and tension and compression loads, and the journal and key parts are subject to large friction and wear. The failure modes are mainly fracture and local excessive wear, and the fracture includes fatigue fracture and overload fracture. Therefore, when selecting materials, the materials should have sufficient strength, stiffness and certain toughness, good wear resistance, high fatigue strength and good machinability. That is, the main shaft is required to have good comprehensive mechanical properties.