In the atmospheric pollutants, there are many harmful gas components that is difficult to distinguish the absorption peaks of different components obtained by infrared and terahertz spectral detection. This paper designs an algorithm for analyzing the proportion of different substances in the measured spectrum based on the theoretical spectrum of the substances that may be included in the measured spectrum. The overdetermined equations constructed by using the corresponding relationship between experimental peaks and different theoretical peaks are solved based on genetic algorithm and simulated annealing algorithm, so the contribution of theoretical spectra of various materials in the experimental spectrum is obtained. In order to verify the accuracy of the proposed algorithm, we use this algorithm to analyze the experimental spectra of the water vapor system composed of known water clusters. The results show that the proposed algorithm can get the specific gravity of different components better and has stronger practicality.