The invention discloses a volumetric flowmeter metering device which comprises a metering coded disc and a sampling control module. The metering coded disc is provided with at least two metering reflection zones, the sampling control module comprises multiple detection devices and a control unit. The metering reflection zones and installing positions of the multiple detection devices divide the metering coded disc into multiple segmentation zones, and position states of the metering coded disc is represented by the segmentation zones detected by the multiple detection devices. In addition, the invention further discloses a metering method of the volumetric flowmeter metering device. By adopting the volumetric flowmeter metering device, the detection frequency is improved, and energy consumption is reduced.