Abstract: 〓Objective  To investigate the expression of micro RNA31(miR31)in colon cancer tissue and its correlation with prognosis，and to study the effect and mechanism of the invasion and metastasis of colon cancer.Methods Pathological specimens of 43 patients undergoing surgical treatment for primary colon cancer.Real time quantitative PCR(quantitative realtime PCR)was used to detect the expression of miR31 in colon cancer tissue，and the relationship between miR31 expression and prognosis and pathological grading was analyzed.The transfection method of liposome mediated transfection was used to transfect human colon cancer HT29 cell line with miR31mimic and miR31 negative control respectively.The effect of miR31 on cell migration ability was detected by scratch test，and the effect of miR31 on cell invasiveness was detected by Transwell test.The effects of miR31 on the Wnt/ betacatenin signaling pathway and the important target gene Claudin1 were detected by Westernblot.〖WTHZ〗Results〖WTBZ〗〓The colon cancer TNM stage Ⅰ ～ Ⅱ expression of miR31 patients was 1.78±0.25,while in patients with stage Ⅲ～Ⅳ was 2.35±0.41（P＜0.05）.The expression of tumor penetrating serosa in patients with miR31 was 2.34±0.47，while that in patients without metastasis was 1.67±0.35（P＜0.05）.The expression of miR31 in patients with lymph node metastasis was 3.49±0.42,expression of miR31without lymph node metastasis was1.64±0.71（P＜0.05）.The expression of vascular invasion in patients with miR31 was 3.31±0.58,that without the occurrence of vascular invasion patients was 2.18±0.63（P＜0.05）.In human colon cancer HT29 cells，the percentage of healing area in miR group(0.74±0.16）was significantly higher than that in NC group（0.43±0.21），the difference was statistically significant(P＜0.05).The number of membrane cells in group miR(182.7±29.3)was significantly more than that in group NC(139.2±25.6，P＜0.05).The expression of epithelial marker Ecadherin in miR group(0.51±0.24)was significantly lower than that of NC group(0.89±0.19，P＜0.05).In addition，activation of betacatenin expression was significantly higher in miR group(1.01±0.23)than that of NC group(0.65±0.24,P＜0.05).The expression of Claudin1 was significantly higher in miR group(0.46±0.17)than that of group NC(0.21±0.12;t=2.69,P＜0.05).Conclusion  miR31 abnormal activates the Wnt/catenin signaling pathway，resulting in overexpression of Claudin1，promoting colon cancer invasion and migration，and affecting the EMT.In colon cancer，miR31 may play a role in promoting cancer.