The invention discloses a standard gas preparation device, which comprises a gas distribution cylinder, wherein a piston is arranged in the gas distribution cylinder. A first air inlet of the gas distribution cylinder is connected with a first gas cylinder through a first gas transmission pipe, and a second air inlet of the gas distribution cylinder is connected with a second gas cylinder througha second gas transmission pipe. The first gas transmission pipe and the second gas transmission pipe are respectively provided with a first gas port and a second gas port, and the first gas port and the second gas port are respectively provided with a first gas bag and a second gas bag. A first valve and a second valve are respectively arranged on the first gas transmission pipe on the gas outletside and the gas inlet side of the first air bag, and a third valve is arranged on the first air port. The second gas transmission pipe is provided with a fourth valve and a fifth valve on the air outlet side and the air inlet side of the second gas bag, respectively. The device can not only flexibly prepare a certain volume of standard gas according to the needs, but also ensure that the pressureof the standard gas meets a standard atmospheric pressure.