AIM: The work was designed to explore protective effects of a traditional Chinese medicine-sini decoction (SD) on liver in hemorrhagic shock and its mechanism relating to oxygen free radical and nitric oxide. METHODS: Anesthetized Wistar rats were subjected to a hemorrhagic shock protocol for 60 min followed by intravenous injection with normal sodium chloride solution or SD solution. Superoxide dismutase (SOD), malondialdehyde (MDA) and nitric oxide (NO) in liver were examined. The inducible nitric oxide synthase (iNOS) was determined immunohistochemically. RT-polymerase chain reaction (RT-PCR)was used to assay the mRNA, which were corresponding to eNOS (endothelial nitric oxide synthase) and iNOS. RESULTS: The activity of SOD decreased, while the concentration of MDA increased in liver during hemorrhagic shock. SD enhanced SOD activity and inhibited a increase in MDA level in liver ( P