To investigate the clinical efficacy and metabolomic effects of Liuwei Dihuang Capsules in type 2 diabetes mellitus(T2DM) patients with yin deficiency syndrome.Methods:A total of 60 patients diagnosed with T2DM with yin deficiency syndrome at Dongzhimen Hospital，Beijing University of Chinese Medicine，from September 2022 to June 2023 were selected and randomly divided into a control group and an observation group，with 30 cases in each group.Both groups received standard treatment，with the control group receiving a placebo and the observation group receiving Liuwei Dihuang Capsules for 4 weeks.Clinical efficacy and metabolomic changes were compared between the two groups.Results:The effective rate in the observation group was 76.67%，significantly higher than that 50.00% in the control group(P<0.05).Metabolomic analysis showed that after treatment，levels of phenylalanine，glutamate，and sphingosine decreased(P<0.05)，while arginine levels increased(P<0.05) in the observation group compared to the control group.Differential metabolites were primarily enriched in pathways including the tricarboxylic acid(TCA) cycle，2-carboxylic acid metabolism，C5 branched-chain dicarboxylic acid metabolism，carbon fixation in prokaryotes，glyoxylate and dicarboxylate metabolism，and the biosynthesis of various secondary metabolites.Conclusion:Liuwei Dihuang Capsules effectively improve clinical efficacy in T2DM patients with yin deficiency syndrome and regulate their metabolic profiles.