There are two clinical causes of hyposmia: one is due to symptoms caused by local factors in the nasal cavity; the other is due to symptoms caused by abnormalities in the olfactory nerve. Patients need to go to the hospital for detailed examination of electronic rhinoscopy, head CT, and MRI to be able to make a clear diagnosis, as follows: a. Local factors of nasal cavity: often seen in obstructive etiologies, such as chronic rhinitis, deviated nasal septum, nasal polyps, and nasal fibrovascular tumors. When the abnormal tumor blocks the olfactory region of the middle nasal tract, the airflow cannot pass through, which will lead to the patient’s decreased sense of smell. In terms of treatment, local surgery is needed, and the sense of smell can be restored after the blockage is removed. Most of the symptoms are caused by local tumor compression. Patients will also suffer from headache, dizziness, nausea, vomiting, olfactory inversion and other related symptoms.