Plate heat exchanger (PHE) freshwater generators are wildly applied at ocean vessels for freshwater supply. In this paper, based on the thermodynamics principle of PHE, a distillation desalination device was designed and manufactured. Water production rate of the investigated PHE device was tested to obtain an optimized setting. The experimental results showed that, the heat source water temperature at inlet and flow rate are the two major factors that affect the freshwater generator performance. Basically, freshwater production rate is linearly with the increase of heat source water inlet temperature increases (60-74℃) and flow (2 000-3 900 kg/h). Feed water flow has an optimal value of about 150 kg/h, and the water production rate increases with the feed water flow below the optimal value. Feed water flow did not increase the rate of water production significantly while the feed water flow over the optimal value, and even led to the decrease of the water production rate. The obtained data can provide empirical reference for the design and optimization of PHE devices.