In view of the constant pressure water supply control system, applied the model predictive control method to modeling and simulation. The method used weighted recursive least squares method with forgetting factor to identify the consequent parameters of model online and to overcome the influence of model mismatch on the control performance; The nonlinear model of water supply system was converted into linear time-varying state space model, and on the basis of the model, achieved the prediction of model output. Through the rolling optimization obtained the optimal predictive control input constantly, and the feedback correction process improved the output precision. The simulation analysis verified the sensitivity and accuracy of the method in water supply.