In order to explore the influence of the position of the water inlet device on the hydrodynamic characteristics of the single-drain rectangular arc angle aquaculture tank, a new parameter, the relative inflow distance C/B (C is the horizon distance from inlet to sidewall, B is the width of the rectangular tank) was proposed in this paper, and the complex flow field of near the sewage outlet were analyzed by fluid dynamics characteristics variables, and to measure the effective utilization rate of water in aquaculture tank, the effective utilization coefficient of energy ηe is put forward. Meanwhile based on the Reynolds averaged Navier Stokes (RANS) equation and RNG k-ε turbulence model, a three-dimensional numerical model of rectangular arc angle aquaculture tank was constructed. Computational fluid dynamics simulation technology was used to calculate and analyze the flow field environment in the constructed aquaculture tank. By adjusting the layout position of the inlet system, the flow field in the tank (especially at the bottom) was optimized, and the influence of the optimization of hydrodynamic conditions on the collection and discharge performance of the aquaculture tank system was analyzed. This base case is validated against the experimental velocity measurements using Acoustic Doppler Velocimetry (ADV) at predefined locations across the central vertical plane of the tank. On this basis, the hydrodynamic conditions of the aquaculture tank system were systematically analyzed by hydrodynamic characteristics, such as the average velocity, energy efficiency, velocity distribution uniformity at the bottom of the tank and so on. The numerical simulation results show that the average velocity and energy efficiency can be significantly improved by optimizing the relative inflow distance, which is conducive to the formation of uniform and stable flow field. And increasing the relative inflow distance parameter C/B from 0.00 to 0.05 can effectively improve the flow field characteristics in the aquaculture tank, and setting the relative inflow distance parameter C/B between 0.02 and 0.04 is beneficial to obtain the best flow field conditions for the single channel rectangular arc angle aquaculture tank system.The results show that the ratio parameter C/B in the range of 0.02~0.04 could effectively improve flow field characteristics of the system so as to get better hydrodynamic conditions for circulating aquaculture, and relatively minor construction changes could improve the hydrodynamic conditions of the aquaculture system and open up new ideas for obtaining the hydrodynamic environment conducive to fish welfare and production operation.