Vemurafenib is a selective and potent small molecule inhibitor of the V600 mutant form of the BRAF protein used in the treatment of melanoma and colorectal cancer. However, vemurafenib has less effect in BRAF mutant colorectal cancer due to the resistance of tumor cell to vemurafenib. To verify whether or not miR-145, a short RNA molecule of microRNA which has been supposed to be a tumor suppressor, is involved in this process, we established vemurafenib-resistant cell line colo205/V and found that the miR-145 expression was significantly downregulated in colo205/V cells compared to normal colo205 cells. Moreover, the overexpression of miR-145 could increase the sensitivity of colo205/V cells to vemurafenib both in vitro and in vivo. In conclusion, miR-145 might be used as a therapeutic target in the treatment of colorectal cancer patients with BRAF V600E mutation.