Methane is a dangerous gas for humans and ambience, and methane gas leak detection is especially significant in colliery, petrochemical, gas tank zone, gas station as well as any other safe fields. The fundamental of Tunable Diode Laser Absorption Spectroscopy(TDLAS) was introduced, the center wavelength at 1 653.72 nm was selected for the absorption of methane detection. Also, a 14 cm optical path reflection cell with micro-lenses was designed. The on-line detection system was tested with the 0-100% methane. And also, it can be used to monitor different positions with a beam splitter. In order to improve the signal-noise ratio(SNR), wavelet transform was used to reduce noise of absorption signals. The detection limit was 335 ppm(1 ppm=10-6). A comparison results between the homemade multi-point full-range laser methane sensor and the commercial infrared gas detector were proved that the system has many advantages to meet the requirements of the majority of industry monitoring, such as: the good stability, full range, fast response, calibration free, safe latent, anti-electric magnetic interference, low cost etc.