Objective To explore the efficacy of tentorium cerebelli hiatus incision for treatment of severe brain injury complicated with tentorial herniation. Methods Tentorium cerebelli hiatus incision was performed in 38 patients of severe brain injury with secondary brain stem damage resulted from tentorial herniation after intracranial hematoma evacuation and bone flap craniotomy decompression. The changes of four sides cistern, ambient cistern and interpeduncular cistern before and after operation were observed. Results There was a siginificant difference in the appearance ratio of four sides cistern, ambient cistern and interpeduncular cistern between the preoperation and postoperation(P