Objective：The purpose of this study was to examine the expression and biological role of miR-939 in human non-small cell lung cancer（NSCLC）and epithelial-mesenchymal transition（EMT）progress. Methods：Quantitative real-time polymerase chain reaction（qRT-PCR）was used to detect the expression of miR-939 in NSCLC. Transwell analysis was used to determine the effect of miR-939 on cell invasion. EMT-related markers were detected by Western blot. Results：The expression of miR-939 in NSCLC tissues was significantly higher than that in adjacent non-cancerous tissues，and closely related to TNM staging and lymph node metastasis. Meanwhile，compared with normal lung epithelial cells，the expression of miR-939 in NSCLC cell lines was also significantly increased. The invasive ability of miR-939 cells was obviously decreased after down-regulation of miR-939 expression（P <0.05）. In addition，miR-939 down-regulation caused E-cadherin increasing and Vimentin decreasing. Conclusion：miR-939 may serve as an adverse factor to promote cell invasion，thus affecting the development of NSCLC.