Abstract: According to the dynamic stress and static stress including line method of the reducer casing fatigue stress cycle,the fatigue test loading scheme was determined,and according to the design load spectrum and flight test,the load state of each load point was determined,and the fatigue test load spectrum was programmed. According to the stress form of the reducer casing,the design of reducer casing fatigue test device was completed. The results show that the test device can not only take dynamic load of high frequency into consideration,but also simplify the fatigue test of the loader,obviously shortening the period the fatigue test takes.