Objective To study the protective effect and mechanism of Inonotus obliquus polysaccharide on liver injury induced by isoniazid( INH) combined with rifampicin( RFP) in mice. Methods Forty-eight mice were randomly divided into six groups ( control, model, huganpian, Inonotus obliquus polysaccharide at low, middle, and high dose ) . The mice were administered orally with isoniazid and rifampicin simultaneously except the control. After 2 h,the control and model groups were administered with normal saline,and others were treated with huganpian and Inonotus obliquus polysaccharide,respectively,once a day for 2 weeks. The liver index and serum levels of ALT and AST,malondialdehyde(MDA),superoxide dismutase(SOD) and glutathione peroxidase( GPx) were measured. Pathology examination of liver tissue was performed. Results The activities of ALT and AST, liver index, content of MDA in liver homogenate of mice treated with Inonotus obliquus polysaccharide and huganpian decreased obviously, while the liver SOD activity increased. Histopathological exzamination showed that Inonotus obliquus polysaccharide alleviated the degeneration and necrosis of hepatic cells. Conclusion Inonotus obliquus polysaccharide shows protective effects on mice with hepatic toxic injury induced by isoniazid and rifampicin,which maybe due to its antioxidation effect.