Objective:To analyze the chem. composition of traditional Chinese medicines by UPLC-QTOF-MS,and explore its application in the evaluation of quality stability of traditional Chinese medicines. Methods:Moluodan concentrated pill samples were determined by ultra-high-UPLC-QTOF-MS,combined with principal component anal.,the quality stability of Moluodan concentrated pill was evaluated by comparing and analyzing of the 10 different batches of Moluodan concentrated pill. Results:A total of 367 chem. constituents were identified in Moluodan concentrated pill by UPLC-QTOF-MS. By comparing and analyzing the chem. composition types and quantities of 10 different batches of Moluodan concentrated pill,it was concluded that the average repetition rate of chem. components in different batches of drugs reached 92%,and the overall quality was stable by principal component anal. Conclusion:In this study,liquid chromatog.-mass spectrometry combined with PCA anal. laid a foundation for the overall quality evaluation of Moluodan concentrated pill,and provided new detection methods and ideas for the anal. of the constituents of Chinese medicines.