The power matching between engine and hydraulic system is inefficient，causing huge waste of energy. In order to solve the question，a kind of power matching control system of hydraulic excavator was designed. In the system, the technologies of engine speed control，working condition control, speed sensor power control, auto idle control were integrated. The characteristics of the system are various, including practicability，energy saving，blocking design，convenient maintenance and so on. It is proved that the precision of speed is high and the biggest speed error is 17 r/min when the excavator has empty load. In the auto idle mode, the response speed switching between high speed and lower speed is quick and the longest adjusting time is about 25 s. The input power of hydraulic pump is matched the output power of engine，the engine speed is steady and the biggest value of fall velocity is within 200 〖JP〗r/min, the average waste of energy is reduced by 56% at least when the excavator is working.