To enhance the hydraulic system efficiency of excavator, one system which adopted the novel hydraulic transformer (NHT) was proposed to control boom cylinder due to the great recoverable energy of boom. Firstly, according to the tough working period, especially for the load fluctuates frequently and violently, the rod side of the boom cylinder was connected to the high pressure line of common pressure rail (CPR). Moreover, the proposed system was analyzed by using of mathematical method and the model was constructed. Measurement data about the boom load change of one excavator was input into the simulation model. Finally, the valid angle range of NHT was studied and the pressure feedback loop was applied. Results showed that the proposed system possessed good servo performance under great fluctuating load. 