Objective To investigate the mechanism by which deubiquitinase constitutive photomorpho⁃ genic⁃9 signalosome subunit 5（CSN5）regulates HCC growth. Methods Through Real⁃time PCR，Western blot and Immunohistochemical staining，the expression of CSN5 and MAT2A in HCC tissues and HCC cells was detect⁃ ed. EdU assay was used to examine the proliferation capability of HCC cells. Results CSN5 was found to be signif⁃ icantly upregulated in HCC tissues and cells. CSN5 downregulation in HCC cells contributed to the cells′ inability to grow. CSN5 inhibition reduced methionine adenosyltransferase 2A expression and inhibited HCC cell prolifera⁃ tion. Conclusion CSN5 regulates HCC cells proliferation through MAT2A.