Abstract: Influenced by external magnetic interference, bottom tracking bias due to bedload movement and instrument precision, the accurate azimuth and reference of boat velocity are difficult to establish and even incorrect when measured by a acoustic Doppler current profiler (ADCP), which causes ADCP flow measurement to be invalid and thus limit ADCP application. To overcome the shortcomings of the traditional ADCP measurement, this paper puts forward a new method of high-accuracy ADCP measurement by means of an external sensor array. The assignment of the external sensors such as GPS compass array or fiber optic gyrocompass was studied and the resettlement program determined. Calculation models for parameters such as the installation error of ADCP transducer, the attitude parameters (roll, pitch and heading) of vessel, the absolute vessel velocity and the azimuth of ADCP transducer are provided. Based on these parameters in reference to the ADCP measurement principles, a set of new models for determining ADCP flow velocity by replacing the absolute vessel velocity, azimuth and attitude provided by ADCP with those provided by the external sensors were developed. The proposed method and models are validated by an experiment conducted on the Yangtze Estuary. These experimental results show that this proposed method improves the accuracy of the measurement of flow velocity, and enhances the range of applications for ADCP measurement.