Abstract: The basic principle, process and key techniques of real-time substructure testing (RST) method are introduced. Linear numerical model of the servo-hydraulic system including translation function and state space form is described. The sliding mode control method and its application to RST of the hydraulic servo experiment system are presented. Finally, simulations of RST with the PID control method and the sliding mode control method are carried out. Results of the simulations with the excitation of El Centro earthquake wave show that: (1) the control accuracy and robustness of the sliding mode control method are better than that of the PID method, (2) the dynamic characteristics of the system have great influence on testing results, and the influence is related to the computation time interval, stiffness and damping of the specimen.