Objective To investigate the changes of nitric oxide content and inducible nitric oxide synthase (iNOS) activity in rat brain tissues after explosive craniocerebral wound and observe the influence of emodin on these changes. Methods After rats were subjected to electric detonators, emodin (10 mg/kg) was injected intraperitoneally at 10 minutes. Water content of brain tissues was measured by using dry-wet methods. The content of nitric oxide and the activity of iNOS were measured at 2, 4, 12 and 24 hours respectively after wound by means of nitrade reductase and colorimctrie method. Results The content of nitric oxide and the activity of iNOS kept at a high level (P<0.01). The content of nitric oxide and the activity of iNOS in model group were increased significantly and reached peak at 2 hours after wound. While the content of nitric oxide and the activity of iNOS in emodin group were significantly lower than that in model group (P<0.01). Conclusion Emodin plays a role in decreasing water content of brain tissues and inhibiting activity of iNOS and may exert a protective effect on brain injury during pathological course after explosive craniocerebral wound.