Abstract: Rotational positive displacement flowmeter is widely used in domestic natural gas trade. The authors consider that based on the measurement principle, the metered flowrate in operation condition is between the transitional flowrate qt and the maximum flowrate qmax. In this paper, the maximum allowed error in flowmeter and the corresponding relationship between the transitional flowrate and the range are analyzed. In accordance with relevant national standards, the technical requirements on flowmeter in appearance, anticorrosion, anti-explosion, checking and configuration are presented. Besides, the paper describes the operation condition, installation requirement, relevant configuration, start-up procedure and maintenance and calibration regulation, and provides the calculation methods about volume flowrate, mass flowrate and energy flowrate. Also, it explains the flowrates and the estimation method of relevant parameters' uncertainty. The topic about how to enhance the accuracy and stability of natural gas metering is also discussed.