The utility model discloses a natural gas orifice flowmeter's diagnostic system, including the diagnostic control ware with through the remote control terminal of LAN with the communication of diagnostic control ware. The diagnostic control ware includes: central controller, verification standard signal generator, standard signal measured module and the communication module of setting on printed circuit board. Checking standard signal generator's input and being connected with the central controller electricity, the output is connected with the signal circuit electricity among the natural gasorifice flowmeter, checies standard signal generator and is used for providing standard signal source for signal circuit. Standard signal measured module's input and the electricity of the flow computer among the natural gas orifice flowmeter are connected, and the output is connected with the central controller electricity, and standard signal measured module is arranged in measuring the backwardsignal who follows flow computer and acquire. Communication module is connected with the central controller electricity for make secondary meter and remote control terminal among central controller and flow computer, the natural gas orifice flowmeter realize the communication.