Abstract Objective To investigate the effect of different doses of antimicrobial peptide LL-37 on the survival of random dorsal flaps in rats. Methods Seventy-five SD rats were randomly divided into sham operation group, model group, LL-37 low-dose group (0.25 mg/kg), LL-37 medium-dose group (0.5 mg/kg) and LL-37 high-dose group (1.0 mg/kg), with 15 rats in each group. The rat flap model was made with the improved “McFarlane flap” method. Intraperitoneal injection was performed 2 h after surgery, once a day for 7 days, and the general condition of the flap was observed. After 7 days, the survival rate of rat flaps in each group was measured, and the histopathological changes of flaps were observed by HE staining. The microvascular density (MVD) of the flap was detected by immunohistochemical staining. The content of superoxide dismutase (SOD) and malondialdehyde (MDA) in the flap tissue was determined by colorimetric method. The level of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in serum were determined by ELISA. The mRNA and protein expression levels of vascular endothelial growth factor A (VEGF-A) and hypoxia-inducing factor-1α (HIF-1α) in the flap tissues were measured by qRT-PCR and Western blot, respectively. Result Compared with the sham operation group, the flap tissue structure of the model group was seriously damaged, accompanied by a large number of inflammatory cell infiltration. The survival rate of skin flap, MVD, SOD activity and mRNA and protein expression levels of VEGF-A, HIF-1α were significantly decreased (P<0.01). The levels of MDA, TNF-α and IL-6 were significantly increased (P<0.01). Compared with the model group, the flap structure of rats in the LL-37 medium-dose group and LL-37 high-dose group was basically restored, with a small amount of inflammatory cell infiltration. The survival rate of skin flap, MVD, SOD activity and mRNA and protein expression levels of VEGF-A, HIF-1α were significantly increased (P<0.01). The levels of MDA, TNF-α and IL-6 were significantly decreased (P<0.01). However, there was no significant change in the related indexes of LL-37 low dose group (P>0.05). Conclusion LL-37 can promote the survival of random flaps in rats, and its mechanism may be related to reducing inflammatory response, reducing oxidative stress level, and promoting microvascular formation of flaps.