Abstract: With the economic and society development, the hydrological monitoring influenced by the structures, such as bridges and dams, has become a normal situation. In view of the actual situation of the influence of bridge piers on water flow in the upstream of the monitored section, based on the actual monitored data of Acoustic Doppler Current Profiler(ADCP)at Tunxi hydrological station of Xin'anjiang in Qiantang River Basin from 2015 to 2019, the results of transverse velocity distribution monitored in the whole section were analyzed, and the rationality of the vertical velocity distribution measured by the existing constant measurement method was evaluated. The optimization scheme of velocity vertical is proposed, which can provide reference for vertical layout of hydrologic stations under the influence of bridge piers.