In current marine low-temperature distillation seawater desalination plant, an ejector is designed to pump gas and water synchronously so as to reduce device size and energy consuming. In this paper, an ejector design scheme with two stages was investigated. Flow field characteristic of the proposed ejector was simulated to demonstrate that this design could increase inlet flow velocity and pressure which in turn could improve inlet vacuum and decrease vacuum. Real experiments were also carried out to validate the simulated results. The experimental results show that, when the flow velocity is larger than 3.5 m/s, vacuum at ejector suction can reach 92% and 90% respectively and meet the performance requirements of marine ejector.