Aim To investigate the protective effect and probable mechanisms of Lumbrokinase on cerebral ischemia. Methods Using a mouse model of acute cerebral ischemia by ligating bilateral arteria carotis communis, the effect of Lumbrokinase on survival time was observed. The rat model of middle cerebral artery occlusion (MCAO) was established to measure infarction area, water content, nitric oxide (NO) content, nitric oxide synthase (NOS) activity and total-antioxidation capability (T-AOC) of brain after 24 h MCAO. Results Lumbrokinase 4 mg/kg significantly prolonged the survival time of mice (67.8±28.4 min) compared with that of the control group mice (9.5±4.4 min) (p<0.01). The infarction area obviously decreased and the reduced T-AOC caused by ischemia was improved in all Lumbrokinase groups (p<0.05 or p<0.01). The 3～6 mg/kg group showed decrease in cerebral water content(p<0.05). Lumbrokinase 6 mg/kg could also decrease NO content and NOS activity to 2.5±0.4 μmol/g and 718±68 U/g respectively (p<0.05). Conclusions The results indicated that Lumbrokinase plays a protective role on cerebral ischemia by decreasing infarction area and water content. The decrease of NO content and NOS activity and the improved T-AOC after ischemia may all contribute to the protective role.