Abstract: Deep-sea aquaculture has developed rapidly in the world in recent years. Aquaculture equipment is required for large-scale, mechanization, automation, and intelligence. Among them, the vacuum fish pump has been used widely in the process of fish catching and conveying. However there is a large range of strong vortexes in the tank during operation, leading to the mutual friction and collision injury between fish. In this study, the structure of the tank and the operation mode were improved to reduce the fish injury for the high working efficiency using a improved fish pump. The inlet pipe passed through the bottom of the tank and then entered the inside of the tank. A trumpet-shaped diversion structure was placed upside down at the top of the inlet pipe. An industrial centrifugal pump was selected as the driving device to replace the water ring vacuum pump. The water inlet of the centrifugal pump was connected to the water outlet of the tank. The fish-water mixture entered the tank, where the fish was separated from the water, due to the suction effect of the centrifugal pump. The incoming fish stayed in the tank, but the incoming water was discharged from the tank by the centrifugal pump. The baseline ratio of fish to water was 1:1 in the pool and the tank. When the ratio of fish to water in the pool was 1:2, 1:3, 1:4, and 1:5, respectively, it was calculated that the conveying time of the improved fish pump was reduced by 20.4%, 30.6%, 36.8%, and 40.8%, respectively, compared with the vacuum fish pump for conveying fish with the same quality. The numerical simulation was carried out to compare the water absorption of the vacuum and the improved fish pump using computational fluid dynamics. The results showed that there was a small vortex range in the tank of the improved fish pump, indicating the weak vortex intensity. An improved fish pump prototype was also designed and then manufactured to verify the numerical simulation in the performance experiments. Compared with the performance of the vacuum fish pump prototype, there was a relatively small vortex in the tank of the improved fish pump, and the conveying capacity did not changed with the change of fish lifting height. The improved fish pump was more friendly to fish conveying. The probability of fish injury was greatly reduced as well. The findings can provide a strong reference for the design of a large fish pump.