In order to study the dynamic characteristics of the hydrostatic secondary control load simulation system, the numerical simulation models of secondary unit were given by using MSC.Easy5 software. It is an efficient way to describe state-oriented discontinuities and to facilitate efficient numerical integration of the secondary control systems. The comparative analysis of the results of numerical simulation and test on frequency response characteristic of speed controlled unit demonstrated the simulation models of secondary controlled system were adequately accurate. The speed variation for a jump in torque on a typical test bench where the speed controlled unit was coupling with the torque controlled one via specimen has been discussed. Simulation result showed that the mechanical coupling had little effect on hydrostatic secondary control load simulation system. The speed variation of the speed controlled unit was mainly affected by load disturbance. Depending on the principle of structure invariance, an approximate feed-forward compensator was designed to resist load disturbance and promote the control quality.