Abstract: In the mine of gas and coal spontaneous combustion coexistence, the whole process of coal spontaneous combustion with concealment and burstiness, has been one of the important reasons contributed to the gas explosion. Most coal spontaneous combustion gas compositions are the same class with CH₄, lighter than air, and easily mixed with CH₄ and O₂, itself will explode. In the whole process of coal spontaneous combustion, the quantity of gas and smoke production in smoldering phase is the biggest and difficult to detect, which is the dangerous phase to cause gas explosion. Under the conditions of low gas, the quantity of gas production of coal spontaneous combustion has " concentration effect " relative to CH₄ emission, which is one of the reasons of gas explosion accidents under this condition, and is also one of reasons of gas explosion accidents without CH₄ explosion concentration detected by gas detector.