ObjectiveTo investigate the relative content changes of differential metabolites and reducing sugars during the processing process of Rehmanniae Radix Praeparata （RRP） processed with Amomi Fructus （AF） and Citri Reticulatae Pericarpium （CRP）， and to lay the foundation for revealing the processing principle of this characteristic variety. MethodThe samples of the 0-54 h processing process of RRP processed with AF and CRP were taken as the research object， and their secondary metabolites were detected by ultra performance liquid chromatography tandem quadrupole time-of-flight mass spectrometry （UPLC-Q-TOF-MS）. The 0.1% formic acid aqueous solution （A）-acetonitrile （B） was used as the mobile phase for gradient elution （0-1 min， 1%-3%B； 1-10 min， 3%-9%B； 10-15 min， 9%-12%B； 15-22 min， 12%-18%B； 22-31 min， 18%-24%B； 31-35 min， 24%-100%B； 35-36 min， 100%-5%B； 36-40 min， 5%-1%B； 40-45 min， 1%B）， column temperature was 40 ℃， injection volume was 3 μL， flow rate was 0.3 mL·min^-1. Electrospray ionization （ESI） was used to scan and collect MS data in the negative ion mode， the scanning range was m/z 50-1 250. Data analysis was carried out using PeakView 1.2 software， and the chemical composition of RRP processed with AF and CRP was identified by combining the literature information and chemical composition databases. The MS data were normalized by MarkerView 1.2， and then the multivariate statistical analysis was applied to screen the differential metabolites， and the changes of the relative contents of the differential metabolites with different processing times was analyzed， finally， correlation analysis was performed between the differential metabolites， the change of the reducing sugar content was combined to determine the most suitable processing time of RRP processed with AF and CRP. ResultA total of 121 compounds were identified from RRP processed with AF and CRP at different processing times， and 12 differential metabolites were screened out by multivariate statistical analysis， including catalpol， hesperidin， isoacteoside， acteoside， narirutin， echinacoside， isomartynoside， decaffeoylacteoside， 6-O-E-feruloylajugol， dihydroxy-7-O-neohesperidin， jionoside D， and rehmapicroside. With the prolongation of processing time， the relative contents of these 12 differential metabolites and reducing sugars changed slightly at 52-54 h. ConclusionUPLC-Q-TOF-MS can comprehensively and accurately identify the chemical constituents of RRP processed with AF and CRP at different processing times， and the suitable processing time of 52-54 h is determined according to the content changes of different metabolites and reducing sugars， which provides a basis for revealing the scientific connotation of the processing principle of this variety.