Objective:To study the risk factors for ipsilateral severe hearing impairment in patients with hemifacial spasm (HFS) after microvascular decompression (MVD).Methods:MVD was performed in 3700 patients with HFS, admitted to our hospital from October 2007 to August 2020; according to the existence of ipsilateral severe hearing impairment, these patients were divided into severe hearing impairment group and non-severe hearing impairment group. The clinical data of these patients were compared. Multivariate linear regression analysis was used to determine the independent influencing factors for ipsilateral severe hearing impairment.Results:Forty-five patients (1.2%) had ipsilateral severe hearing impairment after MVD; no one got recovery of hearing impairment during the follow-up period (0.6-11.8 years, 6.3 years in average). As compared with those in the non-severe hearing impairment group, patients in the severe hearing impairment group had significantly older age, significantly higher percentages of male patients, and patients with left HFS, hypertension, and diabetes mellitus, statistically higher percentage of patients having small posterior fossa volume, arachnoid thickening and adhesion, and vertebral artery compression, significantly lower percentage of patients with anterior inferior cerebellar artery compression, significantly higher percentage of patients with arteriosclerosis of offending arteries and difficult decompression ( P<0.05). Multivariate linear regression analysis revealed that hypertension, vertebral artery compression, arteriosclerosis of offending artery and difficult decompression were independent risk factors for severe hearing impairment in patients with HFS after MVD. Conclusion:It's difficult to get recovery for severe hearing impairment in patients with HFS after MVD; this complication is much common in patients with hypertension, vertebral artery compression, arteriosclerosis of offending artery or difficult decompression.