The combined power and desalination system can improve energy utilisation efficiency and market competitiveness of the production process by adjusting production planning according to the demand load of water and electricity. In this paper, the scheduling model is proposed that addresses the operational optimisation of the combined power and desalination system. The time-dependent electricity price is considered and the proposed model is described as a nonlinear programming (NLP) problem with the maximising total economic benefits. Based on the periodic characteristics of demand load of water and electricity, the typical day of each season is selected as one scheduling time, which is divided into several time intervals according to the change of electricity price. A case study is adopted to demonstrate the presented scheduling model. The results showed: the multi-stage flash (MSF) system keeps running for the total scheduling cycle and the water production varies between 2,000 t/h and 4,000 t/h. A part group’s module of reverse osmosis (RO) system would be shutdown/start up following the increasing/decreasing demand for electricity. When the electricity price higher, the more electricity is supplied to the users and the less water is produced. While the electricity price lower, less electricity and more water are produced. The surplus water is stored in the tank to make up for high water demand. Comparing with the stand-alone plant, the load fluctuation of the power plant decreases from 150 MW to 20 MW. The operation stability and efficiency will be improved by the optimal scheduling of the combined power and desalination system.