To investigate the clinical effect of Modified Dachaihu Decoction（大柴胡汤加味）combined with pioglitazone in the treatment of type 2 diabetes mellitus and its influence on vascular endothelial function.

A total of 114 patients with type 2 diabetes mellitus admitted from January 2022 to June 2023 were included in the study.The patients were divided into single drug group and combined traditional Chinese medicine group by random number table method，with 57 cases in each group.The patients in the single drug group were treated with pioglitazone，while those in the combined traditional Chinese medicine group were treated with pioglitazone combined with Modified Dachaihu Decoction.One case fell off in the combined traditional Chinese medicine group，and the data of each group was compared，including efficacy，blood glucose indexes such as glycosylated hemoglobin（HbAlc），fasting blood glucose（FPG）and 2 hours postprandial blood glucose（2 h PG）before and after treatment，changes in TCM syndrome scores，oxidative stress indexes such as malonaldehyde（MDA），superoxide dismutase（SOD），glutathione peroxidase（GSH-Px）and hemodynamic indexes such as early reverse diastolic blood flow peak velocity（PRV），systolic peak velocity（PSV），end-diastolic blood flow velocity（EDV）and arterial pulse index（PI），and adverse reactions.

The therapeutic effect of combined traditional Chinese medicine group was better than that of single drug group（P<0.05）.The levels of HbAlc，FPG and 2 h PG，TCM syndrome scores，the levels of MDA，SOD and GSH-Px，the values of PRV，PSV，EDV and PI and other indexes were not significant in two groups before treatment（P>0.05）.After treatment，The levels of HbAlc，FPG and 2 h PG，TCM syndrome scores，the levels of MDA，SOD and GSH-Px，the values of PRV，PSV，EDV and PI and other indexes were improved in both groups.The levels of HbAlc，FPG and 2 h PG，TCM syndrome scores，the levels of MDA，SOD and GSH-Px，and the values of PRV，PSV，EDV and PIin the combined traditional Chinese medicine group were better than those in the single drug group（P<0.05）.The adverse reaction rate of the combined traditional Chinese medicine group and single drug group was lower（P>0.05）.

Modified Dachaihu Decoction combined with pioglitazone has significant clinical effect in the treatment of type2 diabetes mellitus，which can effectively reduce the blood sugar level of patients and improve clinical symptoms and hemodynamics of patients，and the treatment has fewer adverse reactions，which is relatively safe.