Objective: To explore the clinical characteristics and risk factors of severe hearing impairment in patients with sudden hearing loss (SHL). Methods: According to the types of hearing curves, 148 patients with SHL were divided into flatness group (n=46), low-frequency group (n=42), high-frequency type group (n=26) and total deafness group (n=34). The clinical relevant data and hearing efficacy in all groups were compared. According to the severity of hearing impairment, patients were divided into severe group (n=53) and non-severe group (n=95). The risk factors of severe hearing impairment were analyzed. Results: There were significant differences in vertigo, history of diabetes mellitus and cerebral infarction, sleep disorders and hearing efficacy among the four groups (P < 0.05). Regression analysis showed that age ≥ 60 years, body mass index (BMI) ≥ 24 kg/m2, hypertension and sleep disorders were all risk factors of severe hearing impairment in SHL patients (P < 0.05). Conclusion: There are significant differences in various clinical data among SHL patients with different types of hearing curves. Age ≥ 60 years, BMI ≥ 24 kg/m2, sleep disorders and hypertension are all risk factors of severe hearing impairment.