This study was conducted to test the effects of schizandrin B (Sch B) on clozapine (CLZ) induced chronic liver injury in mice and the mechanism of action, and this may provide a new approach for clinical prevention of CLZ-induced side effects. The CLZ was given to mice for three weeks alone or co-administration with Sch B. The changes of alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and antioxidation indexes superoxide dismutase (SOD), malonic dialdehyde (MDA), glutathione (GSH) and liver histological evaluation were determined. Expression of Nrf2 was assayed in hepatic cells by immunohistochemical staining and Western blotting. The changes of relative gene expression of NAD (P) H:quinone oxidoreductase l (NQO1) and heme oxygenase 1 (HO-1) were assayed by real-time Q-PCR. The results showed that pretreatment with a lower dosage of Sch B (25, 50 mg·kg^-1) prevented CLZ-induced liver injury as indicated by the reduced levels of ALT, AST and ALP, and the preserved activities of SOD, GSH and inhibiting MDA. It was shown that Sch B could up-regulate Nrf2 expression leading to nuclear accumulation of Nrf2 to induce oxidative response genes such as NQO1 and HO-1. These results suggest that Sch B could protect against liver injury induced by CLZ via the activation of the Nrf2/ARE signal pathway in a dose-dependent manner.