A laboratory trace gas metering device, which is composed of a gas purification unit, a metering collection unit and a control unit. The gas purification unit includes an air inlet pipe, a drying column, a desulfurization column and an inlet electromagnetic valve. The drying column is filled with desiccant, and the desulfurization column is filled with Filling with desulfurizer; the metering and collecting unit includes U-shaped metering tube, constant temperature water bath, gas outlet solenoid valve, outlet pipe of gas outlet solenoid valve and gas collection bag. The U-shaped metering tube is filled with metering liquid, and the U-shaped metering tube is placed in the constant temperature water bath. ; The control unit includes a liquid level controller, an air inlet solenoid valve control switch, an air outlet solenoid valve control switch, an electronic reader and a power supply. The advantages of the present invention are: the metering device is simple in structure, convenient to manufacture and install, low in cost, easy to implement, high in accuracy of the metering method, and strong in applicability. The rate can fully meet the laboratory research requirements.