Zinc is often deficient in patients with liver cirrhosis, and treatment with zinc provides short-term improvement in protein metabolism. However, the long-term effects of zinc have not been fully clarified. Zinc deficiency is common in cirrhosis and has been involved in the altered nitrogen metabolism. To control the increased BUN the effect of Zn supplementation is studied. The cirrhosis patients were divided in to two groups, the control group was given all routine medicines, but the experimental group was given 3-month oral zinc sulfate supplementation (600 mg/d). Plasma zinc levels were measured in all patients and only those patients were selected for study who had serum Zn was lower than normal. Among patients with type C liver cirrhosis were contacted between June 2015 and January 2016, those with a serum albumin level ≤ 3.5 g/dL and a serum zinc level ≤ 70 μg (1.07 μmol)/dL were selected. The urea clearance was observed significantly increased after Zn supplementation. Psychometric tests improved, as did routine and dynamic liver function tests. Also, the plasma concentration of lipid peroxides was reduced by zinc. No significant changes were observed in the control group. The study indicated that long-term oral zinc speeds up the kinetics of urea formation from amino acids and ammonia. Changes in the hormonal drive and/or the antioxidant activity of zinc might be involved in the general improvement in liver function, whereas the beneficial effects on encephalopathy might stem from decreased ammonia. However, although zinc may play a role in hepatocarcinogenesis, the precise implications remain to be clarified.