In order to achieve dynamic balance in a re-circulating aquaculture system (ＲAS)，the idea of“oppo-sing flow”and the principle of Venturi air entrainment were adopted，and 15 experimental conditions were deter-mined to investigate the effect of opposing flow on the aeration in water with different Venturi settings． The results show that the volumetric mass transfer coefficient of oxygen is proportional to water flow rate，but is inversely pro-portional to Venturi setting depth at the same flow rate． By comprehensively considering the aeration effect and the re-circulating opposing flow characteristics，it is suggested that Venturi aerator should be set as A—B stagger layer at the beginning and the end of cultivation，while it should be switched to A—C stagger layer in the mid-term culti-vation．