Abstract: The axle is one of the most important components directly relating the safety operation of vehicles. However, the testing method of axle on site used in China is backward and inefficient, while checking failures occur now and then. But the theory of reliability design of fatigue, which has been well developed, is difficult to be applied to the test of axle on site. In recent years, the computing automotive technology is advocated at abroad to solve the complicated problem of how to put the reliability analysis of fatigue into practice.This paper realized the 3D simulation of testing system through the Pro/E software as well as constructed the system, which was based on the trailer axle testing system prototype. The system hardware was comprised of support, guide, sensors, AC servo motor and servo driver; meanwhile, the system software adapted the modularized idea in order to divide the monolithic construction into five parts, including main operation control module and 4 testing modules. Every testing module was constituted by 5 submodules. The system software program was written by LabVIEW. It drove the linkage device by controlling the rotation of the servo motor and loaded the simulated axle through two pressure heads, then the displacement and pressure were collected as feedback through the data acquisition card. The displacement-voltage linear relationship of A/B pressure head was obtained through experiments on displacement sensors before system test. By calibrating the straight-line equation, the result was that the maximum locating relative error is 5.207%, and the absolute value of average relative error was 1.4%. The voltage-load linear relationship of A/B pressure head was obtained by accurate positioning of load. Analyzed by software SPSS, in the equation of the load stress and voltage linear regression, the result was that R > 0.994, Sig. < 0.05, thus regression was significant.According the constructed testing system, the performance of fatigue, stiffness, strength, and stress of the simulated axle were tested and analyzed. In fatigue test, flaw occurred after 821 times vibration and efficacy was lost after 1067 times vibration; in stiffness test, spot D almost stayed unchanged and the displacements of spot C and E ranged from 60 to 63 mm; in strength test, the maximum displacement of sensor E was 66.622 mm; in stress test, the maximum displacement of spot E was 66.751 mm, and the maximum stress was 259.444 MPa. The system was steady. The simulated test had been lasting for one month and no bug was found. Therefore, the result generally meets the project requirement.