In order to solve the calibration problem of high-pressure hydraulic oil flowmeter for civil aircraft, a high-pressure hydraulic oil flow standard device is developed. The standard device uses a high-pressure plunger pump to provide flow source. The flow rate and pressure of the flow device can be adjusted in a wide range by means of frequency conversion speed regulation and proportional control valve. A piston-type volume tube is used as the main standard in the standard device to realize the flowmeter calibration under high-pressure conditions. The calibration test of cylindrical gear flowmeter under variable pressure condition is carried out by using this standard device. The difference between the flowmeter coefficients under high pressure condition and atmospheric pressure condition is more than 5%, which proves the importance of the research on flowmeter measurement performance and correction method under high pressure and variable pressure. The establishment of this standard device provides an effective means for flowmeter calibration and measurement performance research under high pressure, and it has practical value.