Methane monitoring and alarm system is very important because it guarantees the coal mine production safety. After analyzing impact factors on methane monitoring, this paper established a mathematical model of gas detection system and introduced the key technologies for maintenance-free is dynamic adjusting of system state, auto-zero, auto calibrations of nonlinear and post-processing of the data. The hardware architecture of the mini intelligent methane sensor based WSN (Wireless Sensor Network) and the automatic and visualized calibration technologies of intelligent methane detecting system are described in detail. Finally, the experimental data is analyzed. The system improved the detection accuracy, prolonged calibration cycle of the methane measuring device and lessened the working strength on calibration.