Abstract: To improve the durability of heavy tractor rear axle,the durability problem,such as rod-bracket failure,welding line and straight seam-weld crack was focused to be solved.Attempting to replace the welded axle with cast steel axle,several projects were carried out including the durability comparison between cast-steel axle and welded axle,the development of a virtual test platform for vehicle axle,and the virtual-test model examination by contrast experiment.A vibration fatigue analysis method was applied to solve cast-steel axle and welded axle life,and the bench test was taken to verify the simulation result.The simulation and test results identically show that the cast-steel axle is better than welded in fatigue life,the heavy tractor assembled with cast-steel axle can improve its structure reliability effectively.