Coriolis mass flowmeters are used in custody transfer of oil products stored in oil depots. Its measurement accuracy can be affected by improper installation of the meter. In order to resolve this problem, through the experiment comparing the measurement results of repeating the on-site improper installation of the meter with that of the standard installation, both are set up in the laboratory, it is found that the reason that affects the normal measurement performance of the Coriolis mass flowmeter comes from the stress generated during the improper installation. Through standard installation, the accuracy of product oil measurement is improved by eliminating stresses and by avoiding additional errors. Standard installation of Coriolis mass flowmeter to the specified procedure can effectively enhance its measurement performance.