The resonant photoacoustic spectroscopy gas sensor based on distributed feedback(DFB) diode laser operating at 1.65m was described. The sensor had many advantages such as high selectivity and sensitivity, on-line and real time measurements, compact size and low cost and so on. The response characterizations of the sensor were experimentally investigated. The comparison of the two approaches, amplitude modulation and wavelength modulation, were carried out. The methane (CH) in air was measured with this sensor and the detection sensitivity of 100 ppbv was obtained.