Abstract Background Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, especially in China, with high metastasis and poor prognosis. Recently, as the core component of the polycomb repressive complexes 1 (PRC1), chromobox protein homolog 8 (CBX8) is considered as an oncogene and prognostic marker in HCC. Methods A tissue microarray of 166 paired HCC and adjacent non-tumor samples were collected to identify the relationship between CBX8 and epithelial mesenchymal transition (EMT) associated proteins by Spearman correlation analysis. Knock-down of CBX8 in HCC cells was conducted to detect the biologic functions of CBX8 in HCC metastasis. Results We found out that CBX8 was over-expressed in HCC and its expression was closely related to the metastasis of HCC patients. In addition, knock-down of CBX8 was found to inhibit the invasion and migration ability of HCC cells. Moreover, there was a significant relationship between expression of CBX8 and EMT associated proteins both in HCC cells and tumor tissues. Conclusions Our results indicate that CBX8 promotes metastasis of HCC by inducing EMT process.