The invention provides a natural gas flowmeter verification system. A critical flow nozzle device is a measurement standard device, and transmits a measured value to a module combination. An electricsucking pump provides a gas source, and extracts gas of a stagnation container, to make the container have certain vacuum degree. The module combination acquires temperature, pressure, and humidityof the position of the stagnation container, and temperature and pressure of the position of a natural gas flowmeter examined meter, and transmits signals to a PLC processor to process and takes partin flow error calculation. The PLC processor transmits processed temperature, pressure, and humidity values, and a corrected measured value of the critical flow nozzle device to an upper computer controller. The upper computer controller displays information transmitted by the PLC processor. The natural gas flowmeter verification system is flexible and universal, and is advantaged by high reliability, good anti-interference capability, simple use, good function, and small volume.