Objective · To study the expression of microRNA-143 (miR-143) in human colon cancer and adjacent normal tissues, and to explore its effect on the function of colon cancer cells and downstream target genes. Methods · Lentiviral expression vector of miR-143 was designed and used to stably transfect colon cancer cell lines HCT116 and RKO. Real-time PCR was used to detect the expression of miR-143 in colon cancer, adjacent normal tissues, HCT116 cells and RKO cells infected with lentivirus. The apoptosis ratio of HCT116 cells and RKO cells was detected by Annexin V-APC single staining and flow cytometry. The migration ability of HCT116 cells and RKO cells was detected by Transwell method. The expression of FOSL2 protein was detected by Western blotting assay. Results · The expression of miR-143 in colon cancer tissue was significantly lower than that in adjacent mucosal tissue (0.339±0.454 vs 1.003±0.003) (U=16.000, Z=-4.231, P=0.000). By up-regulation of miR-143, apoptosis rates were significantly higher in HCT116 and RKO cells than those in the negative controls (P=0.000). The count of migrating HCT116 cells in up-regulated group was significantly lower than that in the negative control group (P=0.000). The count of migrating RKO cells in down-regulated group was significantly higher than that in the negative control (P=0.003). By down-regulation of miR-143, the expression of FOSL2 protein was increased. Conclusion · The expression of miR-143 was significantly decreased in colon cancer tissues. Up-regulation of miR-143 can promote the apoptosis rate in both cell lines, and inhibit the migration ability of HCT116 cells. Down-regulation of miR-143 could promote the migration ability of RKO cells. By inhibiting miR-143, the expression of FOSL2 protein in colonic cancer cells would be increased.