Abstract: The determination on gas pressure threshold value of coal and gas outburst has always been a difficult technical problem which affects safe production of coal mines. Before determining threshold value of gas pressure, it generally adopts the reference value 0.74 MPa from Coal and Gas Outburst Prevention Regulations in coal mines. For this limitation, combining with the comprehensive hypothesis about coal and gas outburst, using the theoretical results of elasticity and mechanics, it establishes a physical and mechanical model of coal and gas outburst, proposes a new determination method about the pressure threshold value of coal and gas outburst. The results show that this method has broad applicability, overcomes the blindness of copying the Coal and Gas Outburst Prevention Regulations,has a certain guiding significance for coal mines to prevent coal and gas outburst.