Abstract: A dynamic analysis model considering actuator response delay and compensation strategy is established for a real-time dynamic hybrid testing system with finite-elements based numerical substructure. The delay-dependent stability conditions of several examples are investigated using the root locus technique and further verified by numerical simulations. The results show that the delay obviously affects the performance of inherent modes. A test can be guaranteed to be stable only if the mass of the physical substructure is smaller than the critical value. The third-order polynomial prediction compensation may significantly improve the performance of inherent modes, but its influence on the system stability conditions is related to the instability mechanism.