Objective To analyze the causes, clinical characteristics, risk factors and imaging features of perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSH). Methods The clinical data of 11 patients with PNSH treated were analyzed retrospectively in our hospital from January 2012 to January 2015. All the patients had CT manifestations of perimesencephalic cistern hemorrhage,with DSA and CTA were negative. The clinical features, risk factors and imaging features were summarized. Results 11 cases were confirmed as subarachnoid hemorrhage by skull CT scan in onset 72h in this group. The hemorrhage center mostly located in anterior brain stem cisterns and anterior midbrain interpeduncular cisterns were the majority, including 2 cases in of crural cistern, 1 case in prepontile cistern, 7 cases in interpeduncular cistern and 1 case of lateral ventricle occipital hematocele, without visible intracerebral hematoma. 1~2 weeks later, the reexamination showed that SAH was basically absorbed, in which 2 cases of ventricle were gradually expanded, without special symptoms. Conclusion PNSH belongs to the category of benign diseases. The symptoms of the patients are mild and the CT findings are special, which can be used to discriminate ASH, and hypertension and smoking are the risk factors influencing inset of PNSH.