ObjectiveTo investigate the mechanism of impeded wound healing by exogenous hyaluronan (HA). Methods Wound healing models were established on 18 adult rabbit ears, which were randomly divided into 3 groups, the 2% HA treated-group (group A), the 1% HA treated-group(group B), and the PBS control-group (group C). The process of wound healing was observed morphologically and histologically. The expression of α-smooth muscle actin in fibroblast was measured by immunohistochemical method. Results ①The mean values of wound healing time of groups A, B and C were (11.7±0.6), (11.3±0.6), and (10.8±1.0) days respectively. Wound contraction was greater in group C than in group A and group B. ②Compared with PBS controls, the collagen fibril was slender and arrayed regularly in HA treated wound. ③ The expression of α-smooth muscle actin was greater in group C than in groups A and B. Conclusion It is one of reasons of impeded wound healing that exogenous HA inhibits the expression of α-smooth muscle protein and wound contraction. There exists dose-dependant effect.