Acoustic Doppler point flow meter/flowmeter for river, nullah, pipeline and other scenarios, online monitoring of the flow rate, water level, temperature, instantaneous flow, cumulative flow of the waters. The instrument uses ultrasonic Doppler principle to measure the flow velocity, ultrasonic time difference method or hydrostatic method to measure the water level, and by setting the cross section, the flow rate is calculated. Doppler flow meter has the characteristics of compact structure, no rotating parts, long life, easy to use and maintenance-free, and its widely used in sponge city, water supply/drainage network, black smelly water body, natural river, open channel, reservoir, flow field analysis of scientific research, liquid level detection and other scenarios.