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Considering energy saving and typical working condition of construction machinery, a two-level idle-speed control system based on hydraulic accumulator was proposed to ensure the quick pressure rising at inlet of working chamber of actuator when the idle speed was canceled and the actuator started a new working cycle. The mathematical model of the proposed idle speed control system was developed. The values of the two-level motor speed were obtained according to motor response and characteristics of the pump. The rules of motor speed switch between the two-level idle-speed and the normal working speed were made by detecting the pressures of joystick, pump, two chambers of actuator and accumulator. The parameters of the hydraulic accumulator which was the key component of the idle-speed control system were analyzed through simulation. The experiment was carried out on a 1.5t hydraulic excavator driven by electric power using the obtained parameters of hydraulic accumulator. The comparisons between the idle speed control system with and without hydraulic accumulator and the system without idle speed control were carried out on the testing. The test results showed that the proposed two-level idle-speed control system worked well. Compared with the system without idle-speed control, the proposed control system with hydraulic accumulator can save up to 36% energy. While compared with the idle-speed control without hydraulic accumulator, the inlet pressure of the actuator was raised more quickly and steadily in the proposed control system. This indicated that the proposed system can achieve good energy saving and control performance.