Abstract: The mine statistical method is one of the important methods to the relative gas emission prediction. By using the relationship between relative gas emission and mining depth data to predict relative gas emission, it is found that there is a problem of gas emission change gradient α calculation formula (according to multiple levels actual gas emission data) with the mining depth in the Prediction of Mine Gas Emission (AQ1018-2006) industry standard. In order to solve this problem, a correct mathematical model about the change of gradient α is reduced by using statistical theory of the least squares method. The correctness of the correct change of gradient α is verified by using the actual relative gas emission data in a mine, which has provided a foundation for the application of engineering practice to predict the gas emission with the mine statistical method.