Sulfocompounds is one of the main odor material. A mid-infrared laser based gas sensor is developed for continuous monitoring of the sulfocompounds in pollution emissions. A mid-infrared distributed feedback interband cascade laser (DFB-ICL) is used as light source, and the working wavelength was about of 3.3 μm. A hollow silica waveguide is used for gas cell, and the core diameter is 1000 μm, the length is 5 m. A home-made multi-channel digital lock-in amplifier is adopted to demodulate the 1f and 2f harmonics simultaneously, and calibration-free measurement has been attained by normalized the 2f harmonics with the 1f harmonics. Different wavelength of lasers can be applied to detect methyl mercaptan, dimethyl sulfide, dimethyl sulfide and hydrogen sulfide.