Aim The ischemic cerebrovascular disease(ICVD) has been commonly thought one of the three main causes of death in human.The dangerous factors include hypertension,diabetes,atherosclerosis,smoking,drinking and so on.Smoking has been confirmed independent factor in stroke.Matrix metalloproteinase is one of main enzemy dissolved extral cell membrane.Studies have indicated that matrix metalloproteinase-9 had played an important role in the arteriosclerosis. They all join the appearance of the cerebral infarction.Methods Materials 60 healthy Wistar rats supplied by Department of experiment animal of China Medical University were used.Monocolone antibody of MMP-9 and SABC test box were from BOSTER Biotechnology CO.LTD.Cigarettes were purchased from markets.Method The Wistar rats were divided into 6 groups: normal group(n=6),shorttime and big-dose smoking group(n=12),long-time and big-dose smoking group(n=12),long-time and small-dose smoking group(n=12),giving-up smoking group(n=12),control group(n=6).We obtained brain following experiment ending and observed expression of smoked rat by immunohistochemistry stain.Results Τhe positive substance of MMP-9 showed brown.The expression of MMP-9 in normal group and control group is weak.The significant different expression is observed in other groups(p<0.05).Giving up smoking can reduce the expression of MMP-9.Conclusions Smoking can make MMP-9 express more in endothelial cell.The expression of MMP-9 is dose-dependent and time-dependent.Giving up smoking can reduce expression of MMP-9.The expression of MMP-9 in cerebrovascular endothelial cell may be one of main ways in cerebral infarction caused by smoking.