The invention provides a method for predicting the gas emission quantity of a single coal seam mining area. The method is named as a sourcing proportion method, can be used for predicating the gas emission quantity in the mining area at a mining roadway arrangement stage, and consists of a sourcing method and a proportion method; the sourcing method is used for analyzing and determining the gas source of the mining area; the proportion method is used for actually measuring and summarizing the proportion of each gas source for many times; in addition, the gas mining balance coefficient is summarized and provided, i.e., the coal wall gas emission quantity of a stope face and the coal wall gas emission quantity of an excavation working face have a stable proportional relationship; the proportional relationship is named as the gas mining balance coefficient B. Therefore the coal wall gas emission quantity of the stope face can be predicated by measuring the excavation coal wall gas emission quantity at the mining roadway arrangement stage; further, the gas emission quantity of the stope face and the excavation working face can be predicated through the proportional relationship of each gas resource of the stope face and the excavation working face; further, the goal of predicating the gas emission quantity of the mining region is achieved.