Abstract: The direct method to measure gas pressure process is complex, the success rate is low, the applicable conditions of the indirect method are relatively harsh. Taking Hebi No.3 Mine as an example, based on the experimental law of gas desorption of coal with different moisture contents, the coefficient a of the “Sun Zhongxu formula” is introduced, and a new method that can estimate the gas pressure of coal seams with different moisture contents is proposed. The results show that the “Sun Zhongxu equation” is the best way to fit the desorption curve of coal samples with different moisture contents, the “Sun Zhongxu equation” is determined to be the best fitting formula. The coefficient a can maintain a stable value under different fitting time and has an exponential relationship with gas pressure. The relationship between the coefficient a and gas pressure can be used to estimate the gas pressure of coal seams with different moisture contents. Field verification found that the measured value is close to the theoretical calculation value, the desorption method is feasible to calculate the coal seam gas pressure.