Aiming at the defects of low accuracy, low reliability and large error of ultrasonic flowmeter in low velocity fluid measurement, a four-channel gas ultrasonic flow measurement technology based on DSP is proposed. Firstly, according to the measurement principle of ultrasonic flowmeter, the time difference method is selected as the flow measurement algorithm.Secondly, the acoustic channel layout scheme of the ultrasonic flowmeter is determined, and the weighting coefficient of the instantaneous flow is calculated by using the mathematical integration method. TI′s TMS320F28335 DSP chip is selected to complete the system hardware design. Finally, the received signal is filtered to simulate the flow in the pipeline under static and quantitative conditions.The experimental results show that the average measurement errors of each acoustic channel in the static flow measurement of pipeline are 0.142%, 0.217%, 0.273 % and 0.362%, and the error is less than ±0.4 %, which meets the standard requirements. In the quantitative measurement of low flow rate, the average error between the prototype and the standard meter is 0.945%, and the experimental data show that the prototype detection error decreases with the increase of gas flow rate, which also meets the industrial standards and meets the design requirements.