The fire gas detection alarm system based on tunable diode laser absorption spectroscopy (TDLAS) is an early fire alarm technology which has high sensitivity, high resolution, low rate of false positives, rapid response, develops rapidly in recent years and has a broad application prospect. Tunable diode laser absorption spectroscopy using the wavelength tuning characteristics of semiconductor laser, matches the laser wavelength and the measured gas absorption lines, detects fire gas. Laser wavelength tuning is the key technology to ensure gas detection accuracy. In this paper, a laser precision wavelength tuning method is proposed, based on near infrared optical fiber coupling distributed feedback (DFB) semiconductor laser, and experimental results show that can meet the needs of the fire gas detection system.