Due to the simple structure, low energy consumption and low cost, the mechanical enclosed transmission fatigue life test-bench is widely used. With the rising of labor cost in enterprises, the requirement for system of fatigue life test is put forward. With existing closed mechanical transmission based on the fatigue life test-bench, automation renovation was carried out, including the frequency variation of electrical system, hydraulic loading system, measurement and control system, and a high degree of automation, monitoring and control software was designed and developed to implement the transmission tests in the test process, a torque speed automatic control, automatic start or stop, automatic acquisition and storage test data, and other functions. Fatigue life test results show that the system can have high measurement accuracy and automation level, and has broad application prospects.