Objective To investigate the regulation and function of miR-149 in human colorectal cancer cell lines. Methods miR-149 expression patterns were detected in SW620 and LS174T cell lines using quantitative real-time fluorescence PCR (q-PCR) method. And then, the target gene of miR-149 was explored via luciferase reporter assay. The expressions of STAT3 and p-STAT3 mRNA and proteins in CRC cells were detected by q-PCR and Western blot assay, respectively. miR-149 mimics and pEGFP/STAT3 vector were transfected or co-transformation into CRC cells. CRC cells were divided into miR-NC group, miR-149 mimics group and miR-149 mimics + pEGFP/STAT3 group. Proliferation, migration, invasion and apoptosis were determined by CCK-8 assay, wound-healing assay, transwell assay and flow cytometry, respectively. Results miR-149 expression was down-regulated in SW620 and LS174T cell lines compared to that of the normal colon epithelial cell FHC detected using q-PCR methods (P＜0.01). Then, STAT3 was identified as a direct target gene of miR-149 in CRC cells by luciferase reporter assay. Further studies indicated that the introduction of miR-149 was able to down-regulate the mRNA and proteins expression of STAT3 and p-STAT3, suppress cell proliferation, migration and invasion, and promote apoptosis of CRC cells (P＜0.01). However, the over-expression of STAT3 could decrease the inhibiting effect of miR-149 on the proliferation,migration and invasion of CRC cells. Conclusion miR-149 can inhibit proliferation, invasion and migration and promote apoptosis of CRC cells via targeting STAT3. [ABSTRACT FROM AUTHOR]