Abstract: Objective:To investigate the expression of MMP-9 in gastric cancer, para-cancerous tissue and metastastic lymph nodes and to explore its relationship with the clinicopathologic features and prognosis. Methods:Immunohistochemis -try was used to detect the expression of MMP-9 on tissue microarray containing gastric normal mucosa (n=32), para-can -cerous tissue (n= 54), metastastic lymph nodes (n=41), and gastric cancer tissue ( n=189 ). Results: The positive rate of MMP-9 expression was 78.3% in gastric cancer tissues. The positive rate of MMP-9 expression was associated with depth of invasion, lymph node metastasis, Lauren type and degree of differentiation ( P<0.05), but was not associated with sex, age, or tumor size (P>0.05). There was a significant difference in MMP- 9 expression between gastric cancer tissues and metastastic lymph nodes (P<0.05). In metastastic lymph nodes, the positive rate of MMP- 9 expression was higher. The MVD in MMP-9 positive tissues tended to be greater than that in MMP-9 negative tissues, with a statistical significance (P<0.05). Kaplan-Meier survival analysis showed that the survival of patients without MMP- 9 expression was longer than those with positive MMP-9 expression (P＜0.05). COX regression analysis revealed that MMP-9 expression was not an indepen -dent prognostic factor for gastric cancer. Conclusion:The higher expression of MMP-9 involves the occurrence, progres -sion, invasion, and metastasis of gastric cancer. MMP- 9 can be used as a metastatic predictor and prognostic marker for gastric cancer. MMP-9 may promote angiogenesis. But MMP-9 is not an independent prognostic indicator for gastric cancer.