Abstract: This paper gives some methods of field test and evaluation of the performance of the natural gas metering system with the basis of summarizing the test methods of metering instruments relating to a natural gas metering system. Taking a class A trade metering station as an example, the performance of the metering system is tested and evaluated. Through the evaluation, it is found that the ultrasonic flowmeter, temperature meter and flow computer of the station do not reach the accuracy requirements of the class A trade metering station. The application of the on-site evaluation method of the metering system is described with this example, and it is explained that the on-site evaluation of the metering system is necessary. In order to run the system accurately and reliably, it is suggested that an on-site performance evaluation should be carried after getting the traceability of each metering instrument of the metering system.