The invention provides a device for measuring gas leakage amount of an engine crankcase. The device comprises an oil-gas separation mechanism, a pressure control device, a pressure stabilizing box anda flowmeter, wherein the oil-gas separation mechanism is used for collecting and carrying out oil-gas separation on leaked gas in the crankcase; a gas inlet end of the pressure control device is connected to a gas outlet end of the oil-gas separation mechanism, and the pressure control device is used for carrying out pressure compensation on the gas flowing from the oil-gas separation mechanism;a gas inlet end of the pressure stabilizing box is connected to a gas outlet end of the pressure control device, and the pressure stabilizing box is used for stabilizing the gas compensated by the pressure control device; and the flowmeter is used for measuring the gas outlet quantity of the gas outlet end of the pressure stabilizing box. According to the device, a measuring result of the flowmeter is improved, and the replacement frequency of the flowmeter is reduced.