Abstract: Objective:To observe the oxidative damage of rat liver mitochondria induced by different doses of manganese and explore the related mechanism. Methods:Twenty four male SD rats were divided into 4 groups,6 rats in each group,including control group,low dose group,medium dose group and high dose group. The rats in control group were injected normal saline intraperitoneally and the rats in low dose, medium and high dose groups were injected 2 g·kg^-1·d^-1, 8 g·kg^-1·d^-1 and 32 g·kg^-1·d^-1 MnCl₂ intraperitoneally respectively for 30 days. The rat liver tissue was extracted and mitochondria suspension was obtained by differential centrifugation separation to measure mitochondrial PT pore,the degree of mitochondrial swelling,the mitochondrial membrane potential and the content of succinate dehydrogenase (SDH), cytochrome C, hydroxyl radical OH·and glutathione peroxidase (GSH-PX). Results:The mitochondrial PT pore in the four groups was different and the differences had statistical significances(P<0.01); the mitochondrial swelling degree in high dose group was lower than that in control and low dose group(P<0.05); the mitochondrial membrane potential in high dose group was decreased compared with that of other groups(P<0.05-P<0.01); the content of SDH in medium and high dose group was decreased compared with that in control and low dose group(P<0.01) and the difference of SDH between medium and high dose group had statistical significance(P<0.01); the cytochrome C content in high dose group was higher than that in control and low dose group(P<0.05); the content of hydroxyl radical OH·in high dose group was increased compared with that in other three groups (P<0.01); in the same time, the content of GSH-PX in low, medium and high groups decreased compared with that in control group(P<0.05). Conclusions:Manganese can induce mitochondrial oxidative damage. Manganese has the toxic effects on rat mitochondria and the toxic effects induce rat liver mitochondrial PT pore opening,decreasing the optical density of membrane potential and the content of SDH and GSH-PX,increasing the content of cytochrome C and hydroxyl radical OH·significantly.