This paper develops a water load simulator based on impedance control for control design of a wave maker, i.e., this simulator is used to simulate the load acting on the paddle of the wave maker when making waves. In common control design, external loads are often treated as disturbance and are hence ignored in the system model. However, if the load is too large and beyond the system capacity (e.g., that of a wave maker), it could result in system damage. In order to evaluate the controller performance of wave makers before being implemented on the full scale system, the load simulator developed in this paper uses impendence parameters obtained from various wave conditions to simulate the effect of water load. SERCOS III network is applied in this study. The experimental results demonstrate the effectiveness of the developed simulator.