Abstract: To investigate the dynamic alteration of stromelysin-1 (metalloproteinase-3, MMP-3) proenzyme protein expression in the processes of experimental liver fibrosis. The carbon tetrachloride-induced hepatic fibrosis rat models were used. MMP-3 proenzyme protein expression in the different stages of liver fibrosis was measured by half quantitative analysis of Western blot. MMP-3 proenzyme protein expression could be detected in normal rat liver. In the pathogenesis and development of liver fibrosis, MMP-3 proenzyme protein expression level increased gradually, with the expression rate being maximum at an intermediate stage of fibrosis. And it decreased gradually during the late liver fibrosis and at thestage of liver cirrhosis, but remained relatively high levels above normal. MMP-3 might participate in pathogenesis of liver fibrosis and cirrhosis as an important role.