Abstract: Gas content is a common index to test the effect of measures in coal seam area. Reasonable and reliable critical value of gas content is the key to ensure safe production. Taking No. 3 coal seam of Zhongling coal mine as an example, firstly, the critical initial value of coal seam gas content was determined by using W-P and W-(K1 or Delta H2) relationship which was obtained by experimental study, combining gas geological data, production data and gas dynamic phenomena. Secondly, through field investigation, the reliability of the initial value of the critical value was examined, and the initial value was reasonably corrected. Finally, the critical value of gas content was confirmed by expanding application. The critical value of 3 # coal seam gas content determined by this method was 10.0 m3/t. The later production showed that the critical value was reasonable and reliable, which effectively guided the mine safety production.