Background: The role of Centromere protein O (CENPO) in the development of non-small cell lung cancer (NSCLC) is unknown. This study aimed to investigate the potential roleof CENPO in the development of NSCLCMethods: The expression level of CENPO was investigated in both tissues and cell-lines. Celigo cell counting assay, wound-healing assay, Transwell assay and Flow cytometry was used to explore the effect of CENPO on proliferation, migration, invasion, apoptosis and cell cycle of NSCLC. The potential mechanism of CENPO was explored by Human Apoptosis Antibody, also, western blot was conducted to detect the expression of PI3K/Akt/mTOR pathway and cell-cycle related protein (mTOR, P-mTOR, CDK1, CDK6 and PIK3CA). Besides, the effect of CENPO on the growth of NSCLC solid tumors was demonstrated in vivo.Results: Our study suggested CENPO gene overexpression in NSCLC. Reduced CENPO expression substantially decreased the proliferation, migration and invasion ability, and promoting apoptosis and induces cell cycle arrest of NSCLC cell-lines. Preliminary mechanism research suggested reduced CENPO could active apoptosis pathway, suppressing PI3K/AKT/mTOR pathway and down-regulation cell-cycle related proteins.Conclusion: CENPO was up-regulated in NSCLC and played an important role in promoting the progress of NSCLC.