The results of treating fatty liver with berberine showed that: the liver index was decreased, liver histological lesions alleviated and the lipid metabolism and insulin resistance significantly improved, indicating that berberine could be used for the treatment of fatty liver in an effective way. Its mechanism may relieve the “first-strike” due to the improvement of insulin resistance, thereby reducing the fat deposition in liver cells. Relevant literature demonstrated that berberine could promote the repair of islet β-cells, inhibit gluconeogenesis and promote glycolysis and therefore, a hypoglycemic effect can be produced. At the same time, it can reduce sympathetic activity, inhibit the function of the adrenal cortex, reduce gluconeogenesis, slow down the insulin metabolism and increase the sensitivity of surrounding tissues to insulin, and thus, increase the biological activity of insulin and reduce sugar tolerance injury. The effect of improving insulin resistance with berberine can regulate lipid metabolism, reduce TG in the blood and liver tissue, inhibit exogenous TG absorption, accelerate TG excretion, reduce liver TG synthesis, inhibit VLDL synthesis and promote HLDL synthesis. The improvement in lipid metabolism also reduces the oxidative stress, coupled with the anti-oxygenation that berberine possessed, the lipid peroxidation can be inhibited and SOD significantly increases. Also, MDA can be significantly reduced. Thus, the final tissue damage can be reduced and further development of fatty liver can be prevented.