This paper briefly describes the structure，principle and working process of the mobile radar wave on-line current measuring system.The application of the Henglu hydrometric station of the Jiujiang hydrological bureau is taken as an example，by analyzing the stability，application range and comparison with other flow measurement methods，the advantages and disadvantages of the flow measurement system in practice are summarized，and a new method of flow measurement for medium and small rivers under special water conditions is explored.