By using ultra-high performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry，to investigate the changes of chemical composition in Paeonia lactiflora before and after progressed.Methods:Agilent C18 column，0.1% formic acid aqueous solution-acetonitrile gradient elution，volume flow rate 0.3 mL/min，tandem four-stage rod time-of-flight mass spectrometry were used to determine the chemical composition of 10 batches of raw and fried white peony in different producing areas.Results:A total of 40 chemical components were identified in raw Paeonia lactiflora (RPL) and processed Paeonia lactiflora (PPL).Conclusion:UHPLC-Q-TOF-MS/MS technology provides a fast and efficient analytical method for the analysis of chemical constituents in RPL and PPL，which provides a reference for comprehensive evaluation of the quality of RPL and PPL.