Abstract: The residual gas pressure of coal seam is one of the key indexes of regional outburst prevention effect test. The success rate of direct borehole measurement is low, and it is generally obtained by indirect calculation using Langmuir equation, but it has many test parameters, long period and large error. In order to obtain the residual gas pressure of coal seam more accurately and quickly, on the basis of theoretical analysis, the self-built quantitative gas supply device is used to quantitatively compensate the gas volume of the test tank and measure the coal seam gas pressure, and the gas pressure value of coal seam measured by the experiment is compared and analyzed with the gas pressure value of coal seam calculated theoretically and measured on site. The results show that: Under constant temperature (consistent with the temperature of the coal seam), after compensating the gas amount, the gas pressure inside the test vessel exhibited a characteristic pattern of rapid increase−slow decrease−and eventual equilibrium stabilization. The relative error between the experimentally measured coal seam gas pressure value and the theoretically calculated coal seam gas pressure value is 4.46%−9.21%. The relative error between the experimentally measured coal seam gas pressure value and the coal seam gas pressure measured on site is 2.73%−5.56%. Compared with the indirect method of Langmuir equation, this method can exclude the influence of temperature and moisture on the pressure measurement results, and the test parameters are less and the test time is shorter. Compared with borehole measurement, this method does not need to be sealed and is not limited by the location of pressure measurement. The research results can provide a new method for coal mine to accurately and quickly obtain the residual gas pressure value of pre-pumped coal seam, and provide technical support for coal mine gas extraction standard evaluation and anti-outburst measures effect inspection.