In the present paper, the fresh water generating rates were simulated by a nodal method. The performance of liquid ejector was formulated by Bernoulli equation. The heat transfer rate of heat exchanger was expressed by the simple equations. UA value of the first-stage evaporator was got by the design condition. The inlet temperatures of each stages and return water, evaporation rates of each stages and total fresh water generating rates were predicted. By varying the inlet temperatures of hot water and motive water of liquid ejector, the performance and thermodynamic properties were calculated.