Abstract: The gas pressure gradient variation law and the horizontal ground stress distribution law of the tectonic outburst seam would be the major factor affected to the coal and gas outburst. A quantitative calculation model of the seam gas pressure gradient and horizontal ground stress was established. Taking the regional tecto nic outburst seam near No. 236-80 north cross-cut in Tanjiachong Mine as a study object, the FLAC simulation result showed that the seam failure was serious in the re gion with horizontal ground stress approached to zero. The calculation showed that when the ground stress was about 3 MPa, the gas pressure gradient in the tectonic seam would have a sudden change. When the horizontal ground stress was over 3 MPa, the gas pressure gradient would rapidly increase in the two regionsof0~ 5 m and 42 ~ 62 m along the strike direction of the seam physical model.