OBJECTIVE： To observe the effects of insulin glargine in type 2 diabetes mellitus patients with poor glucose control by rosiglitazone and metformin. METHODS： A total of 90 patients with type 2 diabetes mellitus with poor glucose control by rosiglitazone and metformin admitted to our hospital from Aug. 2013 to Dec. 2015 were divided into control group and observation group according to random number table， with 45 cases in each group. Control group was given Acarbose tablets 50 mg orally before meal， tid， with maximal dose of 300 mg/d. Observation group was given Insulin glargine injection subcutaneously， qd， with initial dose of 0.15 u/kg， adjusted according to blood glucose monitoring， with maximal dose of 40 u/d. Both group were treated for 24 weeks. The levels of fasting blood glucose， 2 h postprandial blood glucose， HbA1c， fasting C peptide and 2 h postprandial C peptide were compared between 2 groups before and after treatment. The time of blood glucose reaching target and the occurrence of adverse events were recorded， and the incidence of adverse events was calculated. RESULTS： Before treatment， there was no statistical significance in above indexes between 2 groups （P＞0.05）. After treatment， The levels of fasting blood glucose and 2 h postprandial blood glucose in 2 groups were significantly lower than before treatment， and the levels of fasting C peptide， 2 h postprandial C peptide and HbA1c were significantly higher than before treatment； except for fasting blood glucose， above indexes of observation group were significantly better than those of control group， with statistical significance （P＜0.05）. The time of blood glucose reaching target in observation group was significantly shorter than control group， the incidence of nocturnal hypoglycemia， severe hypoglycemia， edema and gastrointestinal reactions and total adverse events in observation group were significantly lower than control group， with statistical significance （P＜0.05）. CONCLUSIONS： The application of insulin glargine in type 2 diabetes mellitus patients with poor glucose control by rosiglitazone and metformin can effectively reduce the levels of blood glucose and HbA1c， and improve islet function with good safety.