The detection of CH4 gas is very important for the prediction of fire in mine. In this paper a technology of CH4 sensor on the disturb mode of optic fiber is introduced. It is showed that CH4 can be detected by the flow of light energy in optic fiber, which is caused by the disturbing technology. The experiments showed that the sensibility and the selectivity for the detection of CH4 are researched. The optic fiber sensor for CH4 is simple and reliable and will have wide application in mine safe.