Fourier transform infrared classical computation method applied to the direct quantitative analysis of multicomponent gaseous mixtures of the organic compounds was described in the paper. For the analysis of multicomponent mixtures a number of important problems, such as select of quantitative optimal peak windows and calibration of the spectral band overlapping between the compounds, had been discussed. The FT-IR software for multicomponent simultaneous determination of up to 10 compounds in a gaseous mixture had been completed. The software can provide two kinds of the linear and nonlinear fits for the calibrating concentrations of the interference components. The accuracy, precision and time of the analysis were satisfactory. The results indicate that the method can be used for the simultaneous quantitative analysis of the multicomponent gaseous mixtures of the organic compounds even if there are serious overlaps of the infrared spectral absorption bands of the compounds.