The simulation model of a pumpcontrolmotor system was established. Research simulation and test verification were carried out of response characteristic of the system. The findings were as follows: the displacement ratio of variable pump was decided by the current singal，the rotational speed of the fixed motor was decided by the current singal and the rotational speed of pump together. The efficiency model of hydrostatic system was performed. Research comparsion and test verification of efficiency characteristic were carried out. The research results show below: the pumpcontrolmotor system has good efficiency characteristic within range of larger displacement, moderate pressure and moderate or higher rotational speed of the pump and the motor.