Abstract: This study aims to research the metabolism of free radical and the influences to liver and renal function of boilers with endotoxemia. Besides the therapeutic effect of aminoguanidine on boilers with endotoxemia were evaluated. 90 boilers were randomly divided into tree groups with 30 in each group. GroupⅠwas the normal control. GroupⅡ and Ⅲ were intravenously injected with lipopolysaccharides and GroupⅢ was intravenously injected with aminoguanidine at 1 h before endotoxin injection. The NO concentration and NOS activity in serum and live as well as blood biochemical index were examined together at 1st, 3rd, 5th, 7th and 9th h post-injection, respectively. Results revealed that the NO concentration and NOS activity rose in both surum and liver, the effect of detoxication and elmination of toxicant of liver and kidney were all decreased in broilers suffer from endotoxemia disease while the activities of synthesis protein and cholesterol were abated too. The effect of aminoguanidine group was better obviously. The experimental results showed that free radical activity was increased and liver and kidney function were injured during endotoxemia in broilers. Aminoguanidine could significantly reduce the harm of free radicals.