Abstract: The mechanism and prevention of coal and gas outburst are investigated based on a rare coal and gas outburst accident in which the seam is shallow,soft,and lows gas.The results show that the accident caused by geological factors.The island area constituted by shallow and extremely thick roof,large area gob,and normal fault provides stress conditions for the accident.Vertical stress caused by the extremely thick roof's weight in the island area provides stress condition for coal seam damage and pregnant of the accident.Stress along the oblique direction provides ballistic performance for accident seam and throw coal.Such characteristics of coal seam as large gas desorption speed,low permeability,soft structure,thickness provides gas condition.According to the mechanism of the accident,the accident prevent and control methods is put forward which should prevent and control from the aspects of geological storage,high stress,gas.