For the demand of multiply gas species detection of tunable diode laser spectroscopy, a novel time-division multiplexing method-time sharing scanning multiplexing method is presented.Based on the wavelength modulation spectroscopy technology, quasi-simultaneously multi-species detection in one system cycle is realized by simultaneous modulating and sequencially scanning multiply lasers. This method is used in infrared laser spectroscopy based gas emission multi-component detection system.Through Quasi-simultaneously detection of CH4 and H2S concentrations, the possible gas emission monitoring is guaranteed.At the precondition of sufficient sensing sensation, the system configuration is simplified.