Abstract: To ensure the metering accuracy of gas under the unbalanced gas consumption conditions, the analysis on calculation method of metering error based on the error theory is made starting from the working principie of orifice flowmeter.Take the gas consumption of Delingha Gas Pipeline section in Sebei-Xi'ningLanzhou Gas Pipeline as an example, the suggestion to decrease the metering error of gas under the unbalanced gas consumption conditions is put forward.