Objective Recently, early intensive insulin therapy was reported to improve b-cell function and induce long-term remission in patients with newly diagnosed type 2 diabetes. However, the possible mechanisms responsible for this disease-modifying effect are still unclear. We retrospectively evaluated clinical characteristics of patients with newly diagnosed type 2 diabetes, who achieved a long-term glycemic control after early intensive insulin therapy. Methods A total of 59 subjects with newly diagnosed diabetes participated in a 12 week course of intensive insulin therapy and followed up for 1year. The patients underwent a 75 g oral glucose tolerance test (OGTT) and an assessment of body composition using computed tomography and dual-energy X-ray absorptiometry before and after intensive insulin therapy. Results According to post-insulin therapy OGTT, patients were categorized diabetes group (n = 31) and non-diabetes group n = 28). At 1 year follow up, all patients with diabetes group was received either insulin or oral hypoglycemic agents. Among patients with non-diabetes group, excluding 2 patients lost to follow up, 11 patients achieved long-term glycemic control without pharmacologic therapy, but remaining 15 patients were maintained pharmacologic therapy at 1 year follow up. There is no significant difference in clinical characteristics at baseline between patients with or without maintaining pharmacologic therapy. Compared to a total of 46 patients with maintaining pharmacologic therapy, b-cell function as identified by the insulinogenic index (P < 0.001) was improved significantly after intensive insulin therapy in those patients with achieving long-term glycemic control without pharmacologic therapy. In addition, the increment of the insulinogenic index (P < 0.001) and a loss of fat mass (P = 0.018) were significant before and after intensive insulin therapy in this subgroup. Conclusion These findings suggest that the improvement of early-phase insulin secretion could be an important mechanism for the maintaining long-term glycemic control without anti-diabetic medication after early intensive insulin therapy in patients with newly diagnosed type2 diabetes.