To accurately design the inlet structure of the factory circular recirculating aquaculture tank， based on the computational fluid dynamics technology， fluent software was used to establish a numerical model to simulate the flow field distribution characteristics of the inlet pipe in the pond under different inlet angles θ， inlet diameter ratio d/r， and inlet height h in this study. The average velocity v_avg and uniformity coefficient U were used as the evaluation indexes， and the inlet structure was optimized and analyzed. On the basis of physical experiments that the numerical model can better simulate the flow field characteristics in the aquaculture pond， the effects of different inlet structures on the flow field were simulated. The results showed that under the same conditions， the maximum v_avg was achieved at θ=40° and the U difference between water layers was minimized； the larger v_avg and U was achieved at d/r=0.1 and the U difference between water layers was minimized； the larger v_avg was achieved at h=100~400 mm and the U difference between water layers was smallest at h=100 mm. It was shown that the flow field characteristics in the pond were in an optimal state when the inlet angle θ=40°， inlet angle d/r=0.1 and the inlet height h=100 mm.