Cu2-xSe nanoparticles (Cu2-xSe NPs) as a new therapeutic drug platform is widely used in disease treatment due to their strong near-infrared (NIR) optical absorption. In recent years, with their continuo expansion of applications in different fields, their own biological effects have received increasing attention. However, little is known about the effect of Cu2-xSe NPs on cancer cell. In this research, we found that Cu2-xSe NPs inhibited proliferation of HepG2 and SMMC-7721 cells and they mainly induced cell cycle arrest at the G2/M phase. Moreover, Cu2-xSe NPs inhibited HepG2 and SMMC-7721 cell migration and lamellopodia formation. Further studies indicated that Cu2-xSe NPs impaired mitochondrial respiration by inhibiting electron transport chain (ETC) complex activity, thus reducing ATP levels. The insufficient energy supply subsequently impaired actin cytoskeleton assembly, ultimately inhibiting HepG2 and SMMC-7721 cell proliferation and migration.These findings suggest that Cu2-xSe NPs may has potentially antitumor activity, which might provide new insights of nanoparticles into specific cancer treatment.&#xD.© 2023 IOP Publishing Ltd.