Ultrasonic flowmeters often require the tube to be filled with liquid when measuring the flow of liquid. However, in practical applications, the liquid often contains gas in the working state, causing measurement errors. In order to be able to correct this deviation, this paper proposes a method of combining multiple sensors for correction. First, the FDT-21 ultrasonic hand-held flowmeter was used to calibrate the flow when the pipe was full of liquid, and then using 38KHz ultrasonic transmission and receiving device was used to measure different gas contents, and the effect of different installation methods on the gas flow measurement was studied, to correct the liquid flow measurement in the horizontal pipeline under gas conditions. Finally, it can be concluded that when the horizontal pipeline is full of liquid flow, It is concluded that that the measurement results of the ultrasonic flowmeter will cause errors when the gas is contained, but the correction method can make it about 2%.