Abstract: The gas content of Haishiwan coal mine is measured by separately using direct measurement and gas extraction statistics.It is found that there is a big difference between the direct method measurement results of gas content and extraction statistics results of gas content.Combined with the laboratory high-pressure and low-pressure CO₂ adsorption and desorption experiments,it is found that CO₂ desorption law of coal samples presents two kinds of different circumstances under high pressure.Due to the field sampling time is greater than the transition time of the two kinds of desorption laws,the CO₂ lost quantity of coal samples is greatly underestimated,and it lead to the result that gas content measurement is too small by direct method.