The most reliable diagnostic basis for subarachnoid hemorrhage includes CT and lumbar puncture. Subarachnoid hemorrhage is a clinical syndrome characterized by severe headache, nausea, and vomiting caused by rupture of blood vessels located at the base of the brain or on the surface of the brain, which allows blood to flow directly into the subarachnoid space. Diagnosis of subarachnoid hemorrhage relies on the positive symptoms and signs of headache and meningeal irritation, but CT and lumbar puncture are the most reliable diagnostic bases. Among them, CT is the preferred examination, in which high-density hemorrhagic shadows can be found in the cerebral pool and cerebral sulcus, and even in the ventricles of the brain. In addition, when the symptoms are typical and CT findings are not abnormal, but subarachnoid hemorrhage is still suspected, lumbar puncture can be used to see bloody cerebrospinal fluid to make a clear diagnosis. It is recommended to consult a medical professional for standardized diagnosis and treatment.