Objective: To investigate the mechanism of lncRNA HCG18/miR-17-5p/HMGA2 axis regulating the proliferation and metastasis of non-small cell lung cancer (NSCLC) cells. Methods: Sixty-two pairs of NSCLC tissues and corresponding para-cancerous tissues collected at Central Hospital of Chengde City from June 2017 to June 2018 were used for this study; in addition, NSCLC cell lines (A549, NCI-H1299, H1650, NCI-H460) and human lung epithelial BEAS-B cells were also collected. mRNA expression levels of HCG18, miR-17-5p and high-mobility group AT-hook 2 (HMGA2) in NSCLC tissues and cell lines were measured by quantitative Real-time polymerase chain reaction (qPCR). Si-HCG18, miR-17-5p, miR-17-5p+HCG18 or pcDNA3.1-HMGA2 were transfected into A549 cells and NCI-H460 cells; CCK-8 assay was used to detect the proliferation of transfected cells, Transwell assay was used to detect the migration and invasion ability of cells, and Wb was used to analyze the expressions of HMGA2 and EMT associated proteins (E-cadherin, N-cadherin and vimentin). The target relationships between HCG18 and miR-17-5p, or between miR-17-5p and HMGA2 were confirmed by dual luciferase reporter gene assay. Mice A549 cell xenograft model with HCG18 knockdown was constructed, and the growth of transplanted tumor was observed. Results: lncRNA HCG18 was highly expressed in NSCLC tissues and cells (all P<0.01); HCG18 level was significantly increased in patients at late stage or with lymphnode metastasis; and high HCG18 level was correlated with poor prognosis and low survival rates of NSCLC patients (all P<0.01). Knockdown of HCG18 significantly inhibited NSCLC cell proliferation, migration and invasion (all P<0.01), up-regulated E-cadherin expression but suppressed N-cadherin and vimentin expression (all P<0.01), and the volume of xenograft was obviously decreased (P<0.05). Dual luciferase reporter gene assay confirmed the relationship between HCG18 and miR-17-5p as well as miR-17-5p and HMGA2. miR-17-5p transfection significantly inhibited NSCLC cell proliferation, migration and invasion (all P<0.01), and up-regulated E-cadherin expression, reversely suppressed N-cadherin and vimentin expression (all P<0.01); however, miR-17-5p + HCG18 transfection reversed the effect of miR-17-5p on NSCLCcells.Conclusion:HCG18promotes the proliferationandmigrationofNSCLCcellsthrough regulating miR-17-5p/HMGA2 axis.