In an automobile, a stable and durable alternator is extremely important. Based on the basic characteristics of the alternators now on the mainstream market, the hardware simulation method was used to build a simulated “car engine-alternator-auto load-the external environment hardware environment” system. High and low temperature humidity test chamber simulates the vehicle internal environment and the inverter driving power frequency conversion is used to simulate motor car engine power system. It uses fixtures, belts, and pulleys to simulate the connection of the engine to the alternator. In addition it uses electronic load cases to simulate automobile electric power consumption with all kinds of current, voltage, speed signal components to provide feedback signals based on the testing system of alternator to make comparisons. The testing system is designed by analyzing and optimizing the structural mechanics of the whole system according to the requirement of the hardware system layout. For each part of the system factors of design were considered included shape, size, material selection process and heat treatment. Parts and detailed drawings were prepared and later sent for fabrication. The tests indicate that hardware alternator testing system has no major defects that can prevent it from being developed for commercial use.