The invention disclose an infrared spectrum identification method and system for polluted gases. The method comprises steps of: extracting characteristics of target gas spectrum under a preset condition, forming a target gas spectrum characteristic data set, and recording the data set as a standard spectral library data set; extracting characteristics of actually measured spectrum of a target gasbased on sparse learning, so as to obtain actually measured spectrum characteristics; selecting spectrum matching the actually measured spectrum characteristics in the standard spectral library data set so as to reconstruct the actually measured spectrum; and determining components of the target gas according to the reconstructed actually measured spectrum. The infrared spectrum identification method and system for polluted gases have characteristics of highly adapting to complex environment under the actual measurement condition and identifying components of mixed gases highly precisely.