Objective To investigate the expression of FOXO3a and MMP 9 in colorectal cancer tissues and their relationship . Methods Tissue microarray and immunohistochemical SP methods were used to detect the expression of FOXO 3a and MMP 9 in 78 cases of colorectal cancer tissues and 69 cases of corresponding normal intestinal mucosa tissues ,then analyze the relation be-tween their expression and the clinicopathologic parameters of the patients ,and the relation between the expression of FOXO3a and MMP 9 .Results (1)The positive expression rate of FOXO3a in 78 cases of colorectal cancer tissues and 69 cases of normal intesti-nal mucosa tissues are 57 .69% (45/78)and 95 .65% (66/69) ,the positive expression rate of MMP 9 in 78 cases of colorectal cancer tissues and 69 cases of normal intestinal mucosa tissues are 85 .90% (67/78) and 15 .94% (11/69) ,and the difference is significant (P=0 .000) .(2)The decreased expression of FOXO3a and the increased expression of MMP 9 in colorectal cancer are significantly correlated with the depth of tumor invasion ,tumor histological differentiation ,metastasis of lymph node and TNM stage (P<0 .05) ,but there is no significant relationship with patients′age ,gender and tumor size (P>0 .05) .(3)There was a negative corre-lation between the expression of FOXO3a and MMP 9 (r=0 .272 ,P<0 .05) .Conclusion The decreased expression of FOXO3a and the increased expression of MMP 9 may be closely related with carcinogenesis ,invasion and metastasis of colorectal cancer ,and their combination may be an important indicator to evaluate the malignant degree and prognosis of the colorectal cancer .