Abstract: Objective: To establish the type 2 diabetes mellitus(T2DM) rat model,and observe the effects of pioglitazone on insulin resistance and function of pancreatic islets in T2DM rats.Methods: Forty SD male rats were randomly divided into the control group(NC group,10 rats) and high-fat group(30 rats).Twenty-four T2DM model rats were established,and randomly divided into the diabetes mellitus group(DM group) and PIO group(12 rats in each group).The levels of body mass(BM),fasting blood glucose(FBG),fasting insulin(FINS),glycosylated hemoglobin hemoglobin-A1c(HbA1c),C-reactive protein(CRP),blood lipid,insulin resistance index,islet β-cell function index and insulin sensitivity index(ISI) were measured in two groups.Results: The levels of BM,TC,TG,LDL-C,FBG,HbA1c,FINS/CRP and HOMA-β index in DM group and PIO group were higher than those in control group(P<0.05 to P<0.01).The levels of HDL-C,ISI and HOMA-β in DM group and PIO group were lower than those in control group(P<0.05 to P<0.01),and the level of HOMA-β in PIO group was higher than that in DM group(P<0.05).Conclusions: Pioglitazone plays a therapeutic role in T2DM rats,which may be involved in reducing insulin resistance and improving islet function.