Abstract: Objective To investigate the expression of endogenetic matrix metalloproteinases-9 (MMP-9) and transforming growth factor-β(TGF-β) and their role in the wound healing of blast injury. Methods Rat models of blast injury under a humid and hot environment were established and the effusion from the wound surface was collected at 4,24,48 h and 5,7,14,21 and 28 days after injury,respectively.The contents of MMP-9 and TGF-β in the effusion of the wound were measured by zymography and enzyme-linked immunosorbent assay (ELISA),respectively. Results During the wound healing of blast injury,MMP-9 and TGF-β exhibited changes that followed a regular pattern,both reaching the peak value at 48 h after the injury.TGF-β content reached the another peak on day 7.TGF-β value and MMP-9 contents decreased in the second week after injury and their reduction was no longer parallel.Administration of tissue inhibitor of metalloproteinase (TIMP) in the early phase of injury showed no obvious effect,but during the 2 weeks after the injury,its administration caused decrease in MMP-9 content and increase in TGF-β content in the effusion. Conclusions In the early phase of wound healing,the elevation of MMP-9 and TGF-β accelerated cell migration to promote the clearance of the inflammatory necrosis tissues,which might be one of the wound healing mechanisms.But overexpression of MMP-9 in the wound may hinder wound healing,and appropriate use of TIMP can accelerate the delayed wound healing.