Abstract: With the increase of natural gas demand, the supply-demand two party of natural gas have a mutually critical condition on the metering accuracy of gas when the gas marketing is conducted. At present, the metering data of supply party is taken as a criterion for gas marketing in the domestic market. However, many factors often influence the gas marketing, which results in remarkable metering errors. In the light of the problem of metering errors, starting from the error theory and taking the gas transmission trunk line as a study object, an analysis on error-induced problem and a feasibility study to reduce the error are made. Take the metering error of the standard orifice flowmeter as an example, the auth ors calculate the metering errors produced in Zhongyuan Oilfield--Ji'nan gas tra nsmission pipeline.