It has been suggested that trimethylation of lysine 27 on histone H3 (H3K27me3) is a crucial epigenetic process in tumorigenesis. However, the expression dynamics of H3K27me3 and its clinico-pathological/prognostic significance in hepatocellular carcinoma (HCC) are unclear. In this study, the method of immunohistochemistry (IHC) was utilized to examine protein expression of H3K27me3 in 2 independent cohorts of HCC tissues and corresponding non-tumorous hepatocellular tissues by tissue microarray (TMA). The optimal cut-point of H3K27me3 expression was assessed by X-tile program. Our results showed that the cut-point for high expression of H3K27me3 in HCCs was determined when more than 70% of the tumor cells were positive stained. High expression of H3K27me3 was examined in 134/212 （63.2%） and 76/126 (60.4%) of HCCs in testing and validation cohort, respectively. Correlation analysis demonstrated that high expression of H3K27me3 in HCCs was significantly correlated with large tumor size, multiplicity, poor differentiation, advanced clinical stage and vascular invasion (P<0.05). In addition, high expression of H3K27me3 was associated closely with HCC patient shortened survival time, independent of serum AFP levels, tumor size, multiplicity, clinical stage, vascular invasion and relapse as evidenced by univariate and multivariate analysis in both cohorts (P<0.05). In different subsets of HCC patients, H3K27me3 expression was also a prognostic indicator in stage II tumor patients (P<0.05). Thus, these findings provide evidence that a high expression of H3K27me3, as detected by IHC, correlates closely with vascular invasion of HCCs and is an independent molecular Molecular Medicine marker for poor prognosis of patients with HCC.