The aquaculture industry is now in a state of changing, from traditional to modern, from extensive to accuracy aquaculture, with Recirculating Aquaculture System as a creative and efficient aquaculture model. In order to investigate the effects of inlet system optimization on the internal flow field characteristics of aquaculture tanks, analyzes the hydrodynamic features of aquaculture tank applying different inlet structure layout, so as to provide a theoretical basis for the inlet structure design of Recirculating Aquaculture System.Under the application of Computational Fluid Dynamics simulation (CFD), a three-dimensional numerical turbulence model of the square arc angle aquaculture tank was constructed. The single tube inlet system was located in the middle of the arc wall of the aquaculture tank (hereinafter referred to as: arc wall single tube), and adjusted to various inlet-diameter ratios (parameter C/B, the ratio of the horizontal distance C from the center of the jet tube to the tank wall, to the length B on the shorter side of the tank) and different jet angles to study the flow field characteristics in the tank system. From the experiment it is found that the internal flow field features of single tube aquaculture tank are significantly affected by the inlet angle and diameter ratio of the inlet system, and the optimized jet angle of each inlet diameter ratio of square arc angle aquaculture tank differs with each other. The layout of the inflow system of the aquaculture tank involves the two parameters of inlet diameter ratio and jet angle in a comprehensive way, and make sure them are matching. According to the relative inflow distance data, the results show that with the increase of inlet diameter ratio, the optimal average velocity curve of water body first increases and then decreases. When the inlet diameter ratio is 0.09 and the jet angle is 25°, the velocity is the maximum. The optimal angular velocity of inlet diameter ratio 0.09 is about 28.13% higher than that of inlet diameter ratio 0.01. When the relative inflow distance reaches 0.07-0.11, the uniformity coefficient reaches the peak value when the jet angle is 25°. According to the comprehensive analysis of the internal flow velocity, flow field uniformity and internal characteristic diagram of the flow field in the aquaculture tank,under the condition that the inlet diameter ratio C/B=0.07-0.09 and the jet angle is 25°, the internal flow pattern of the aquaculture tank is generally better than other working conditions, the flow environment of the aquaculture tank achieves the best, and the correstanking flow conditions accommodate the needs of Recirculating Aquaculture System better, reducing energy consumption and building a steady flow system. This research will provide a basis for influent system of Recirculating Aquaculture System designing and the optimization of its flow field features.