The roots of Polygonum multiflorum are traditional Chinese medicinal herbs in processed form or raw state. Raw Polygonum multiflorum can detoxify and loosen the bowel and relieves constipation, but processed Polygonum multiflorum can benefit blood, hair, strong muscles and bones, turbidness and lipid lowering. The raw and processed Polygonum multiflorum contain chemical components such as stilbene glycosides, anthraquinone and phospholipid, but their contents are different. The toxicity of raw Polygonum multiflorum decreased after processing. The chemical composition, efficacy and hepatotoxicity of raw and processed Polygonum multiflorum are different. It was easy to recognize the difference in appearance between raw and processed Polygonum multiflorum, but it was not easy to distinguish the power of raw and processed Polygonum multiflorum. Therefore, it is necessary to find a fast and simple method for distinguishing them. Mid-IR has the advantages of fast detection speed and nondestructive. Mid-IR has been widely used in the identification of traditional Chinese medicine. This paper aimsf to establish the fingerprint of the mid-infrared spectrum of raw and processed Polygonum multiflorum and identify them by orthogonal partial least-squares discriminant analysis (OPLS-DA). The chemical composition in 38 batches of raw and processed Polygonum multiflorum were determined by mid-IR of 4 000~700 cm^-1, and the characteristic peaks of chemical composition were analyzed. OPLS-DA of simca13.0 software analyzed the data. The mid-infrared fingerprints of 38 batches of polygonum multiflorum from different sources were established, mainly including protein, nucleic acid, fatty acid, anthraquinone, stilbene glycosides and phospholipids. The peak shape and peak intensity of the infrared spectrum were analyzed, and the difference of peak shape between the raw and the processed radix aconitum was less, but the peak strength was different. OPLS-DA was used to establish the infrared spectral difference model of raw/processed Polygonum multiflorum. The results showed that the raw and processed Polygonum multiflorum could be well divided into two categories. The left was raw Polygonum multiflorum, and the right was processed Polygonum multiflorum. SPSS 13.0 statistical software was used to perform the t-test. Constituents with VIP>1 and p<0.05 (t-test) were considered statistically significant. The differential constituents of raw and processed Polygonum multiflorum were stilbene glycosides, anthraquinone and phospholipid. The results showed that the content of stilbene glycosides, anthraquinone and phospholipid were different in the raw and processed Polygonum multiflorum. The differential constituents of raw and processed Polygonum multiflorum found by mid-IR and pattern recognition is consistent with the literature reports. The results showed that this method was feasible. In this study, the medium infrared spectrum was successfully used for the rapid detection and overall quality evaluation of Polygonum multiflorum. Identifying Polygonum multiflorum with Mid-IR and pattern recognition could provide the basis for the quality control and rapid identification of Traditional Chinese medicine. The study can successfully identify theraw and processed Polygonum multiflorum by mid-IR and pattern recognition and provide a reference for quality control and quick identification of TCM.