Abstract: According to analysis of ultrasonic flowmeter measurement principle and combined with measurement status after mixture of two kindsof gas with different gas components in Jinan Compressor Station of SINOPEC Yulin-Jinan Gas Pipeline Branch Company, volumeflow calculation formula for ultrasonic flowmeter is simplified and it is derived that the volume flow and relative density are related tocompression factor ratio Z₀/Z_n under standard conditions and working conditions. With the increase of the gas relative density, the ratio of Z₀/Z_n is increased and the flow measurement value output by the ultrasonic flow meter under standard conditions is also increased. Finally, rationalization proposal is proposed to reduce impact of dual gas source component difference on the ultrasonic flowmeter.