Calibration-free trace detection of acetylene gas is achieved by near infrared tunable diode laser absorption spectroscopy combined with a self-designed cylindrical mirror multi-pass absorption cell. A distributed feedback diode laser emission at 1.53 μm and the cylindrical mirrors multi-pass absorption cell with an effective optical path length of 10.5 m is used. The calibration-free wavelength modulation absorption spectroscopy is used to detect the acetylene, and the Allan variance is used to analyze the system performance. This technology is compared with the traditional wavelength modulation spectroscopy. The results show that compared with traditional wavelength modulation absorption spectroscopy, calibration-free wavelength modulation absorption spectroscopy has advantages of simple structure, high sensitivity, and calibration-free of concentration and optical power, which improve detection sensitivity and measurement accuracy of the system. The measurement error of the technology is less than 5%, and it is 3.5 times that of traditional wavelength modulation technology. The detection sensitivity of the system is 0.127×10 -6 with average time of 1 s, and the detection sensitivity is 0.031×10 -6 with average time of 118 s.