Abstract: To protect the safety mining of protected layer at 1781（3） working face, based on the theory of protective layer mining, 3DEC finite difference software is used to simulate the influence of lower protected layer mining on the protected layer, it is concluded that: based on the clear symmetrical shape in unloading area on the whole, the height of pressure relief range is over the roof area of protected layer, strike pressure relief angle is 102.28° to 112.6°, dip pressure relief angle is 99.31° to 100.09°; at the same time, to obtain reasonable advanced distance of protective layer along the strike direction, we carried out field measurement for protected layer 1761（3） working face gas dynamic parameters, and get that the beginning line and stopping line of protected seam should retreat inside a certain distance with the beginning line and stopping of the protective layer; the fully unloading point is located in rear of the protective layer of 20 m to 120 m. Based on the above conclusion, we determine that arranging floor through beds hole to carry out gas extraction for 1781（3） working face, and verify the extraction effect of protection area, and extraction rate is 62.9%.