Aim To investigate the effect of transfection of recombinant adenovirus vector carrying angiotensin converting enzyme 2 (ACE2) gene (Ad-ACE2) on protecting endothelium, improving insulin resistance and inhibiting liver fibrosis in apolipoprotein E knock-out (ApoE-/-) mice fed with high-fat diet. Methods ApoE-/- mice were fed with high-fat and high-energy food to simulate metabolic syndrome. 30 ApoE-/- mice were randomly divided into control group (Con group), adenovirus empty vector group (EGFP group) and ACE2 gene therapy group (ACE2 group), with 10 mice in each group, and each group was given a high-fat diet. The 3 groups were injected respectively with normal saline, Ad-EGFP and Ad-ACE2 by intravenous injection of the tail vein. At the end of 12 weeks, glucose tolerance test and insulin tolerance test were carried out. After the mice anaesthesia, blood was extracted from heart tip and blood lipid level was measured. Liver tissue was taken with HE staining and oil red O staining. Immunohistochemical staining was used to observe the expressions of ACE2, collagen-Ⅰ (COL-Ⅰ), collagen-Ⅲ (COL-Ⅲ) and interleukin-6 (IL-6) in liver tissue. Results In ACE2 group, Ad-ACE2 transfection significantly increased the expression of ACE2 in ApoE-/- mice liver (P＜0.05). The endothelium-dependent function in ACE2 group was significantly better than that in Con group and EGFP group (P＜0.05), and insulin sensitivity was stronger than that in Con group and EGFP group (P＜0.05), but the level of blood lipid did not change significantly. The COL-Ⅰ, COL-Ⅲ and IL-6 expressions of liver tissue in ACE2 group were lower than those in Con group and EGFP group (P＜0.05). Conclusion ACE2 overexpression can protect the endothelium, improve insulin resistance, inhibit liver fibrosis and thus protect liver function.