Abstract: In order to improve the prediction accuracy of the gas emission value for a longwall coal mining face, from the analysis on the coal mining face length, th e gas distribution in the seam and goaf and the gas content in the top and low adjacent seams and others, the prediction formula of the gas emission value for different length coal mining face was obtained.Taking the longwall coal mining face with a face length of 300 m in Hengtai Mine as an example, according to the actual paramete rs of the coal mining face, the gas emission value of the coal mining face with different advancing forward speed was predicted.The predictions could provide the basis to the rational selection of the ventilation system and the gas comprehensive control.