Abstract: The specimen is assumed to be a rigid mass in the design of the shaking table control system,but in fact,there is a big difference between the specimen and the shaking table system caused by the assumption of the rigid mass of the specimen. This results in the control system operating in a narrow frequency band and poor stability reducing the replaying precision of the recorded seismic waves. In this paper,models are established both for the SDOF and MDOF systems which are designed to be the rigid mass and non-rigid mass,and then,through the analysis of these models,the performances of the control systems are evaluated. The conclusion is that the stability of the system designed for the non-rigid mass performs best in the unloaded condition and the stability of shaking table is greatly improved.