To realize multi-component analysis of air quality detecting,an gas quantitative method combining technique of Fourier Transform Infrared (FTIR) spectroscopy and the method of spectrum subtraction was applied. Based on Michelson micro-interference principle and Lambert-Beer law,FTIR spectrometer coupled with long path White gas cell was used to measure the infrared spectrums of the trace gases,and then,the values of gas concentration was deduced by the method of spectrum subtraction. Furthermore,for the gases to be detected,the regions were chosen carefully to provide optimum detection of the compounds interested with minimum interference by other compounds (especially,vapor and CO₂). The optimal window for CO,SO₂,NO₂,NO and CO₂ would be the regions at 2250～2020 cm^-1,1230～1070 cm^-1,2 940～2 840 cm^-1,1 965～1 775 cm^-1,and around 668.24 cm^-1 respectively. The quantitative analysis for CO,SO₂,NO₂,NO and CO₂ of different concentrations was carried out in this way. Results indicate that the values of relative errors are below 10%.