In this article, a two-stage ejector for the subzero refrigeration system of fishing vessels is proposed, and the optimization design and performance analysis are studied. A two-stage ejector optimization design method based on the flow field parameter matching is proposed to achieve maximum entrainment performance. The computational fluid dynamics (CFD) method is adopted for the ejector modeling and parameter optimization. In addition, the water-cooled condenser is employed to reduce the pressure difference between condenser and evaporator. In this way, the higher entrainment ratio can be achieved. Simulation results show that the proposed two-stage ejector can achieve evaporating temperature as low as 248. 15 K and the optimal area ratios of first and second stage ejector are 11. 8 and 6. 5, respectively. As the intermediate pressure increased from 253 to 324 kPa, the entrainment ratio rises firstly and then decreases. It reaches a maximum value of 0. 096 when the intermediate pressure is 304 kPa, with the coefficient of performance reaching 0. 074. It can conclude that it is energy efficient to utilize the waste heat from fishing vessels to drive the subzero refrigeration system with the optimal designed two-stage ejector and a water-cooled condenser.