To investigate the protective effect of polyethylene glycol (PEG) modified recombinant cytoglobin (PEG-rCygb) on acute liver damage in mice. The acute liver injury model of KM mice was induced by CCl4 and then treated with PEG-rCygb, The liver and blood samples were collected for biochemical and histopathological analysis. The results showed that PEG-rCygb reduced the liver mass index and decreased significantly the levels of alanine amiotransferase (AST) and aspartate transaminase (ALT) in mouse serum. In liver tissues, the content of malondialdehyde (MDA) was decreased, whereas the content of glutathione (GSH) was increased in PEG-rCygb treated group. PEG-rCygb also elevated the activities of total super oxidedismutase (T-SOD) and catalase (CAT) in liver tissues. HE staining of liver tissue slices revealed that PEG-rCygb relieved fatty degeneration of liver, decreased inflammatory factors and reduced liver cell injury. Further in vitro experiments indicated that the protective effects of PEG-rCygb on hepatic stellate cell (HSC) against H2O2 were enhanced compared with that of rCygb. All results indicated that the PEG-rCygb promoted oxygen free radical scavenging ability and prevented acute liver injury in KM mice induced by CCl4.