In order to solve the problem of on-line flow monitoring in the complex environments such as low flow rate and fluctuating backwater,the non-contact radar wave sensor and contact type horizontal ADCP sensor were combined into a complete on-line flow monitoring system basedon the principle of acoustic Doppler frequency shift and radar wave velocimetry, according to the complex hydrologic monitoring condition in the monitoring section of the new Yunliang River into the Dianchi estuary, so that the simultaneousreal -time data acquisition of river water surface velocity and underwater target velocity was realized. Then,the synchronized water surfacevelocity and the underwater index velocity were simultaneously input into the model to simulate the flow field and velocity distribution. After thereal -time flow had been calculated, which was transferred to the central station server through the GPRS channel, the data were analyzed,processed, stored, transcribed and released, so as to achieve the functions of inquiring the remote and real-time flow, working status and etc. inweb and mobile phone app. The one year operation show that the system is normal and stable.