Abstract: Four kinds of calibration methods for flowmeter. that is. prover method,volume methods,weighing method and standard apparatus, are introduced. Based on given correction factors by the State Standard 《GB/T1885-1998》and API MPMS11.1-2004 on calculation of liquid coefficient of thermal expansion, calculation equation for it during flowmeter calibration are deduced, thus calculation errors of petroleum products can be effectively eliminated and accuracy of metering and calibration data can be increased.