To investigate inner ear of patients with sudden deafness with three-dimensional fluid attenuated inversion recovery (3D FLAIR) MRI, and the relationship between the results of 3D FLAIR and the prognosis. Twenty-three patients with sudden deafness received 3D FLAIR at 3T MRI, and the signals of inner ear were recorded. Hearing levels were evaluated at initial visit and after treatment. The relationship between 3D FLAIR findings and hearing prognosis was evaluated. Eight patients with sudden deafness showed high signals in the affected cochlea on 3D FLAIR, the others of affected cochlea and all of contralateral cochlea showed no signal on 3D FLAIR. The age, sex, affected side, period to initial visit and initial audiogram had no difference between cochlea no signal group and high signal group. The average auditory threshold (x±s) in cochlea high signal group (90±21) dB HL was significant higher than that in cochlea no signal group (60±28) dB HL, P<0.05 at patients' discharge. After treatment, in cochlea no signal group, two cases' hearing was complete recovered, remarkable improvement in five cases, slight improvement in two cases and no change in six cases. In cochlea high signal group, hearing was slight improvement in one case and no change in seven cases. The prognosis was significant difference between two groups. Five of seven patients with vertigo and sudden deafness showed high signal in affected side vestibule on 3D FLAIR, and the hearing of whom had no change after treatment. 3D FLAIR can show high signal in affected inner ear in sudden deafness patients, and which is related to a poor hearing prognosis.