Abstract: On the basis of detail study on the burial history of Permo-Carboniferous main coal seams and evolution history of Qinshui basin,the gas generation history and stage gas yield are discussed in detail,and “effective gas generation stage”and “gas yiele in effective stage”are introduced in this paper.The authors consider that the gas generation history and the gas yield in effective stage of seams are the key gas-controlling geological factors,and that the later the generation stage and the larger the gas yield,the higher the gas content of coal seams.