The causes of tinnitus in one ear include secretory otitis media, sudden deafness and acoustic neuroma. 1. Secretory otitis media: Negative pressure in the middle ear due to the dysfunction of the eustachian tube, and the accumulation of fluid in the tympanic chamber, causing unilateral tinnitus, hearing loss, and a sense of ear tightness. 2. Sudden deafness: the etiology of this disease is not yet clear, and may be related to viral infection, rupture of the membrane labyrinth and circulatory disorders. Patients often have unilateral tinnitus, deafness and vertigo, of which tinnitus can be the first symptom, mostly appearing before deafness, so some patients may have the phenomenon of tinnitus in one ear. 3. Auditory neuroma: when the patient has a tumor in the auditory nerve sheath, it can cause tinnitus, hearing loss and vertigo on one side, and a few patients even have deafness, so some patients may have tinnitus in one ear. There are many other causes of tinnitus in one ear, such as cerumen impaction, Meniere’s disease, etc., should be consulted as soon as possible, after the diagnosis is clear, and follow the doctor’s instructions for treatment.