Piston type liquid standard pipe prover

The utility model discloses a piston type liquid standard pipe prover comprising a metering cylinder body assembly, a photoelectric guide mechanism, a hydraulic system and a nitrogen pressure system, wherein the metering cylinder body assembly comprises a metering cylinder body and a metering piston, the metering piston comprises a large piston and a small piston used for opening or sealing a liquid flow passage arranged on the large piston, and the small piston is connected with the large piston through a poppet valve; the photoelectric guide mechanism comprises a positioning frame, a linear guide rail and a metering piston rod, a plurality of photoelectric detection switches are arranged on the positioning frame, one end of the metering piston rod is connected with a pulley mounting seat, a dimmer and a pulley are installed on the pulley mounting seat, and the other end of the metering piston rod is connected with the small piston; the hydraulic system comprises an oil tank, a piston type hydraulic cylinder