OBJECTIVE： To investigate the effects of acarbose combined with metformin on related indexes of patients with type 2 diabetes mellitus. METHODS： A total of 100 patients with type 2 diabetes mellitus were randomly divided into control group （50 cases） and observation group （50 cases）. Control group was given Acrbose tablet 50 mg orally， 3 times a day. Observation group was additionally given Metformin hydrochloride tablet 0.5 g orally， 3 times a day， on the basis of control group. Both groups were treated for 12 weeks. The levels of fasting plasma glucose （FPG）， fasting plasma insulin （FINS）， glycosylated hemoglobin （HbA1c）， 2 h postprandial plasma glucose（2 hPG）， postprandial 2 h insulin （2 hFINS）， insulin resistance index （HOMA-IR）， the proportion of Th cell subsets in CD4+ T cells，IL-22，IL-17A and IFN-γ， mRNA expression of IL-22，IL-17A and IFN-γ were observed in 2 groups before and after treatment. The occurrence of ADR was recorded. RESULTS： After treatment， FPG， FINS， HbA1c， 2 hPG， 2 hFINS， HOMA-IR， the proportion of Th cell subsets in CD4+ T cells， the concentrations of IL-22， IL-17A and IFN-γ， expression of IL-22 mRNA， IL-17A mRNA and IFN-γ mRNA in 2 groups were significantly lower than before treatment，with statistical significance （P＜0.05）； there was no significant difference in the proportion of Th1 in T cells between 2 groups（P＞0.05）. Other indexes of observation group were significantly lower than those of control group， with statistical significance （P＜0.05）. There was no statistical significance in the incidence of ADR between 2 groups （P＞0.05）. CONCLUSIONS： For patients with type 2 diabetes mellitus， acarbose combined with metformin can effectively control the level of blood glucose， improve insulin resistance， balance Th cell subsets， reduce inflammatory factors levels but don’t increase the occurrence of ADR.