Flair sequence is a commonly used sequence for MRI, the full name is liquid attenuation inversion reversal sequence, also known as water suppression imaging technique. It is commonly used in cranial MRI, where the high signal can indicate brain disease such as brain tumors and subarachnoid hemorrhage in pathological conditions, or sometimes as a normal physiological phenomenon. Flair sequences are commonly used in cranial as well as spinal MRI. It suppresses cerebrospinal fluid high signal in the T2 phase, removes cerebrospinal fluid interference, and makes it easier to visualize high signal lesions. Flair high signal can indicate brain tumors, cerebral infarction, cystic lesions in the brain, subarachnoid hemorrhage, cerebral contusions, and other disorders. Certain areas may also show high Flair signal under normal conditions, such as the intracranial hemiovoid center, the radial crown, the posterior limb of the internal capsule, and the medial thalamic system. Flair high signal should be analyzed differently according to different parts of the body, and should be combined with the patient’s clinical manifestations, other examination results, and under the guidance of specialists for clear diagnosis and treatment.