Abstract: Mastering the bottom plate gas enrichment law and effectively arranging gas extraction drilling holes is the key to regional anti-surge using close protective layer mining. Taking the 3# coal seam mining of a mine to protect the 5# coal seam as the engineering background, through the slip line equation and the numerical simulation of unloading mining of the protected coal seam, this paper gets that the fissure development of the bottom plate of the unloading mining of the protected seam is more than the spacing of 18.20 m from the protected seam, which meets the requirements of the vertical distance of the unloading mining. Based on the distribution law of bottom plate fissure evolution in numerical simulation of unloading mining in the upper protected seam, numerical simulation study on the influence of gas pressure and rock permeability on gas enrichment is carried out, and it is obtained that: gas in the protected seam is enriched to the area of unloading fissure development, and the gas pressure in the area of unloading fissure development is at least 16 times higher than that in the area of non-fissure development, and the ratio of gas pressure in the two areas shows a 29-fold linear growth relationship with the initial pressure of gas; with the increase of distance between fissure and coal column, the distance between fissure and coal column increased. With the increase of the distance between the fissure and the coal pillar, the gas pressure in the fissure gradually decreases; the change of permeability of the disturbed rock layer has a sensitive effect on the gas enrichment in the location of the more developed fissure, and both of them satisfy the linear decreasing relationship, with the increase of permeability of the disturbed rock layer, the maximal gas pressure in the area of the fissure decreases from 83% of the gas pressure of the original coal bed to 30%, and the change of the location of the poorly developed fissure is not obvious. Based on the gas enrichment law of the fissure of the bottom plate of the protective layer, the design of extraction drill holes, through industrial tests, shows that: the average concentration of gas in the extraction drill holes in the non-fissure area and the average daily pure volume of gas extraction are only 6%-46% and 4%-45% of that of the gas-enriched fissure area, respectively, and the extraction rate reaches 43%, with a residual gas content of 4.6 m³/t, which is up to the standard of extraction, and it can be demonstrated that gas is enriched into the fissure of the bottom plate of the protective layer, as well as using the fissure of the bottom plate of the protective layer to enrich gas, and using the fissure of the protective layer to enrich gas. This demonstrates that the gas is enriched to the bottom plate fissure of the protective layer, and that it is reasonable to use the bottom plate fissure of the protective layer to arrange the extraction drilling area.