Taking the different tonnage hydraulic excavators as the research objects, the rotary system energy recovery efficiency was calculated, application scope and energy saving effect of accumulator were verified. Choosing the bag type accumulator that was widely used as the energy storage component, the working parameters were obtained, through modeling of rotary system, theoretical calculation and AMESim simulation, energy recycled of the three different tonnage hydraulic excavators were acquired. The simulation results fit well with theoretical calculation, which proves the accuracy of rotary system model. At the same time, the research about energy recovery efficiency of different tonnage hydraulic excavators provides theory basis for enterprise to improve excavator energy saving efficiency.