Abstract: Objective To investigate the effect of topical heparin on alleviating Ⅱ-degree burn pain in rats and related mechanism.Methods A rat model of Ⅱ burn pain at the bottom of the foot was established. Then, blister lavage was performed using low, medium, and high doses of low molecular weight heparin, or OGT2115 was injected into the blister, and pain was observed. The blister was extracted and rat venous blood was collected to measure the concentration of heparanase(HPSE) by ELISA. The location and related quantity of HPSE in local skin were determined by immunohistochemistry and immunoblot. The healing of the skin tissue in each group was observed by Masson staining.Results Blisters were developed on the burning skin, which reached the superficial layer of the dermis, with obvious burn pain. Blister lavage with medium and high doses of low molecular weight heparin and administration of OGT2115 into the blister increased the plantar maximum contact area(P<0.05). The expression of HPSE was detected in the serum and blister fluid. For intact skin, HPSE was locally expressed in the papillary layer of the dermis, while the expression of HPSE was reduced after burning(P<0.05). Compared with the control group, the heparin-affected burn tissue showed poor healing than the control, with lack of a clear structure of the papillary layer.Conclusions Topical heparin can relieve burn pain. HPSE derived from blood is involved in the occurrence of burn pain, which may be the target of heparin for its analgesia.