ObjectiveTo research the metabolism of components in the Radix of Paeonia lactiflora Pall. Methods(①) we established the HPLC fingerprint of water extract of Paeonia lactiflora Pall. and real-time monitored the chemical composition. (②) We established the HPLC fingerprint of rats' serum samples from hepatic portal vein, serum samples from aorta abdominalis and samples of intestinal absorption of Paeonia lactiflora Pall. (③) On this basis, using the established methods, I-IPLC fingerprint spectrum of serum samples,the sample of herb, the sample after intestinal metabolism, rats' serum samples from hepatic portal vein and rats'serum samples from aorta abdominalis were analyzed and compared in order to infer the metabolism of components in the Radix of Paeonia lactiflora Pall. Results24 compositions were detected, seven of which were metabolized by intestinal flora and could not be absorbed into blood; six of them could not be absorbed directedly into intestinal; eight new compounds were absorbed into blood after bowel metabolism while they were not detected in water extract in Paeonia lactiflora Pall. ConclusionWe could infer the metabolic processes of chemicals of Paeonia lactiflora Pall. in oral administration with this method.