Based on the methane absorption spectrum,a versatile sensor for hazardous gases under coal mines was designed by using an open-path gas chamber and the technology of single light beam with multi-wavelengths. Compared with the ocmmercial available methane sensors,it has many advantages,such as full measurement range,higher precision and faster response. And it can be used to analyze the concentration of several components,the explosivity and hazard degree of the mixed gases. And thus,it will offer the accurate information under mines timely in order to avoid accidents.