Abstract: The measurement of flow velocity is usually made by counting pulses occruing in a flow meter in a time interval. However, this method cannot meet the need for real-time monitoring of flow velocity. This paper proposes a design of a flow meter module, which realizes instantaneous flow-velocity detection. The module includes circuits for signal processing, instantaneous velocity detection, and flow detection and a 485 interface. A test platform was built to verify the design. The relationship between the rotational speed of the flow sensor and the original output signal and the relationship between the pulse width and the signal frequency of the flow sensor were investigated. An MCU was used to upload the pulse width to a server to monitor the flow velocity in real time. Experiments showed that the module can detect flow signals with frequencies below 510 Hz in real time, with an error rate of pulse detection less than10⁻⁶.