Abstract: In 2021, China’s consumption of natural gas exceeded 300 billion cubic meters. Even slight measurement discrepancies in such volumes can result in significant economic impacts, and yet, the reliability of currently utilized natural gas flowmeters in the market leaves much to be desired. The ultrasonic flowmeter for natural gas, a non-contact flow measurement device, is widely used but its measurement accuracy is affected by numerous factors. Using the ANSYS simulation platform and considering the geographical location and seasonal characteristics of Xi'an, a numerical model of a DN300 pipeline's four-path ultrasonic flowmeter was established to study the coupling effects of solar radiation factors within the natural gas transmission environment. The time-difference method of the ultrasonic flowmeter for natural gas measures pipeline fluid flow by utilizing the difference in ultrasonic wave transit time. The flow correction coefficient, a key parameter in the metering of the ultrasonic flowmeter, is defined as the ratio of the path-line average speed to the cross-sectional average speed of the pipeline. Simulation results reveal that with changes in solar radiation energy, the relative error of the flow field correction coefficient experiences only slight changes. When the solar radiation coupled air velocity is considered, the relative error range of the flow field correction coefficient with solar radiation in winter is between 0.005% and 0.091%, and in summer it's between 0.048% and 0.27%. The magnitude of change in summer is noticeably greater than in winter. To improve the measurement accuracy of the ultrasonic flowmeter, a secondary correction of the ultrasonic flowmeter device can be carried out at noon during the hotter summer days.