MicroRNAs have been implicated in regulating diverse cellular pathways. Emerging evidence indicates that miR-143 plays causal roles in cancer tumorigenesis as a tumor suppress gene; however, its role in prostate cancer tumorigenesis remains largely unknown. The aims of this study were to verify the effect of miR-143 on proliferation and migration abilities of prostate cancer cells. The expression level of miR-143 and its target gene KRAS were measured by realtime PCR and western blotting, respectively. Effects of miR-143 in cell proliferation, migration and chemosensitivity were evaluated by MTT assay, FACS cell cycle analysis, colony formation assay, and transwell migratory assay. Our results revealed an inverse correlation of expression between miR-143 and KRAS protein in prostate cancer samples (Pearson's correlation scatter plots: R = -0.707, P < 0.05). Moreover, over-expression of miR-143 in prostate cancer cells suppressed their proliferation and migration and increased their sensitivity to docetaxel by targeting EGFR/RAS/MAPK pathway. These findings suggest that miR-143 plays an important role in prostate cancer proliferation, migration and chemosensitivity by suppressing KRAS and subsequent inactivation of MAPK pathway, which provides a potential development of a new approach for the treatment of prostate cancer.