Objective To investigate the effect of topical appl ication of insul in on the burn wound heal ing in aging diabetes mell itus (DM) rats and to explore its mechanism. Methods Seventy-five SPF Wistar rats (female and/or male), aged 12-24 months and weighing 300-350 g, were selected and randomly divided into group A (burn control group, n=25), group B(DM burn control group, n=25), and group C (DM insul in treatment group, n=25). The rats in group B and group C were fedwith high-fat, high-protein, and high-sugar forage for 1 month and received intraperitoneal injection of streptozotocin (STZ)to establ ish experimental model of aging DM. The rats were fed with high-fat, high-protein, and high-sugar forage for another 8 weeks. Then, the deep second-degree burn model was establ ished in the rats of group B and group C. The wounds in group A and B underwent local subcutaneous injection of 2 mL isotonic sal ine and group C received local subcutaneous injection of 0.1 U insul in. The rate of wound heal ing was calculated 7, 14, and 21 days after burn injury. At 1, 3, 7, 14, and 21 days after burn injury, HE staining observation, immunohistochemistry staining for CD34, detection of sugar and hydroxyprol ine (HOP) content in wound tissue, and microvessel density (MVD) calculation were performed. Results At 7, 14, and 21 days after burn injury, the wound heal ing rates of group A and group C was significantly higher than that of group B (P lt; 0.05), and there was no significant difference between group A and group C (P gt; 0.05). Histology observation at 21 days after burn injury: in group A, certain degree of epithel ization was evident in the wound epithel ium; in group B, large quantity of necrotic tissue was evident; in group C, complete epithl ization occurred in the wound epithel ium with better epithel ial cell differentiation and more neonatal collagen. For the sugar content in the wound tissue, group A was significantly lower than group B or group C at 1, 3, 7, 14, and 21 days (P lt; 0.05) and group C was significantly lower than group B at 7, 14, and 21 days (P lt; 0.05). For the HOP content in the wound tissue and the MVD count, group A or group C was significantly higher than group B (P lt; 0.05) and there was no significant difference between group A and group C (P gt; 0.05). CD34 expression: in group A, it was (+) at 7 days, (++) at 14 days, and (+++) at 21 days; in group B, it was (+) at 14 and 21 days; in group C, it was (++) at 7 days and (+++) at 14 and 21 days. Conclusion Topical appl ication of insul in can promote the synthesis of wound collagen, accelerate the woundangiogenesis, and speed up the wound heal ing in aging DM rats.