Abstract: In order to achieve the safe and efficient mining in coal and gas outburst coal seam using the method of field measurement and numerical simulation, studied the liberating effect of stress and gas and gas when the interlayer has thick and intact rock layer. And analyzed the rule of stress change and rock damage. The results show that stress of floor is released which is 43% of in-sute stress and the depth of floor damaged is over 20 meters. The failure occurs in the rear 5m of longwall face. New fractures and old ones generated the gas channel, and gas release effect is obvious. But in the process of mining, goaf residue gas may accumulate in the top corner of air-return way side, mine should strengthen the gas monitoring.

Key words: protective coal-seam, gas migration, FLAC3D, fracture development, "barrier", rock seam, floor damage mechanism