Abstract: Trough the Change scope analysis of the stress and coal quality in Tensional faults,the flow of coal seam gas in tensile fault control area is approximately unidirectional flow.Through formula of gas unidirectional flow,computing formula of gas pressure control boundary in tensile fault was put forward and the influence of tensile fault on coal seam gas in control area was quantified.By using the method to calculate control boundary in F₂ fault of Hongsong coal mine,the calculated result and measured result was basically same.