Abstract: Firstly, the mathematical model of a real-time dynamic hybrid test of a MDOF structure considering the shaking table response delay and compensation strategy is established. Then, as demonstrating examples, the delay-dependent stability conditions of a 2-storey structure and a 3-storey structure are investigated using the root locus technique based on Padé decomposition approximating the delay term. Finally, some tests are performed to validate the obtained stability condition. The results show that because of the delay, a stable test can be guaranteed only if the mass ratio of the experimental substructure to the numerical substructure is smaller than a critical value; a third-order polynomial compensation improves this critical value for a low or middle frequency structure.