ObjectiveTo explore the relation between vascular endothelial growth factor （VEGF） and the formation of tumor thrombosis in the main trunks of portal vein (PVTT). MethodsTumor specimens were collected from 36 patients (16 patients with PVTT, the other patients without PVTT and metastasis) undergoing resection of hepatocellular carcinoma (HCC) and portal thrombectemy, PVTT specimens of 16 patients named group A1, the same patients’ with HCC named group A2, tumor specimens of the other patients named group B. In situ hybridization and immunohistochemistry were used to investigate VEGF mRNA, protein and microvessel density (MVD) on surgical specimens. The intensity was evaluated using a computer image analyzercell analysis system.ResultsVEGF mRNA expression was detected in the tumor’ cell of the specimens. The expression rates of VEGF mRNA in the group B, A2, A1 were 30%, 100%, 100% respectively, and the expression rates of VEGF mRNA in group A2 and A1 were higher than that in group B （P＜0.01）. The intensity of VEGF mRNA in group A2 （0.078 5±0.019 6） were lower than in group A1 （0.194 4±0.059 0） （P＜0.01）. VEGF protein expression was often detected in the tumor cell, vascular endothelial cell and fibroblast cells. Invasion was detected in small vein in group A2, more tumor cell colony detected in group A1. The expression rates of VEGF protein in group B, A2, A1 were same as VEGF mRNA; the intensity of VEGF protein in A1 （0.165 6± 0.034 5） was higher than in group A2 （0.108 1±0.024 3） （P＜0.01）. MVD in group B, A2, A1 was 31.9±14.4, 63.3±15.1, 116±27.6/view of 200 microscopefield, MVD in group A1 was higher than group A2 （P＜0.01）, higher in group A2 than in group B. There was a statistically significant correlation between the intensity of VEGF expression and MVD in group B,A2 and A1. ConclusionVEGF could play an important role in the invasion, metastasis of HCC and the formation of PVTT. Angiogenesis in tumor is correlated well with the progression of HCC.