Diode laser absorption spectroscopy(DLAS)has developed into an important analytical technique,which has been applied to analyze gas concentration in industry,it usually only can measure single gas' concentration.In this work a pair of CO and CO2 lines whoise center frequencies are respectively 6 338.589 5 cm-1 and 6 337.99 cm-1 are selected are tested simultaneously with a diode laser scanning the pair of lines.Wavelength modulation spectroscopy(WMS)and coherent electronic detection techniques are adopted i...