The liquid cross-flow has important influence on bubble formation and aeration is important to flow field characteristics in plug-flow aeration tank.A 3D acoustic Doppler velocimeter (ADV) was used to measure the flow field in an aeration tank of large scale and flow field characteristics were analyzed for the further study of flow field characteristics in aeration tank.The results showed that flow velocity distribution had characteristics of medial small and lateral large after the flow passed bend and cross flow existed.After the flow entered straight, the velocity distribution constantly adjusted and difference between medial and lateral water flow velocity decreased and the deeper shallow water was,the faster flow rate adjusted.Compared with clear water when the aeration plate was open,velocity near the surface decreased and that deep below the surface increased at the aeration plate upstream section,but velocity downstream was opposite. Turbulence intensity after aeration was much larger than that before aeration at the aeration plate downstream section.
