Patient Lai, female, 45 years old, was admitted to the hospital with a sudden onset of headache. The patient had a severe headache with nausea and vomiting, and obvious cervical tonicity; the cranial CT showed subarachnoid hemorrhage; further whole brain angiography confirmed an aneurysm at the beginning of the left posterior communicating artery, the size of which was about 4.3×3.9 mm. On July 19, the whole brain angiogram showed that the aneurysm was completely clamped, and the internal carotid artery and the left posterior communicating artery were kept well open. Cerebral aneurysm is a hemangioma-like protrusion due to abnormal changes of local cerebral blood vessels, which has a great risk of rupture and bleeding and is known as an intracranial “untimely bomb”. Once an aneurysm ruptures and bleeds, the patient is often disabled or dies, and survivors can still bleed again. Craniotomy is the main way to treat aneurysms and prevent them from rupture and bleeding. However, cerebral aneurysms are often hidden deep in the interstices of important nerves and blood vessels in the skull, and the procedure requires high microscopic skills and is difficult and risky, but once successful, it can cure the presence of cerebral aneurysms. This patient had a good surgical outcome and was cured postoperatively without complications.