Objective To compare the efficacy and outcome, and analyze the possible causes of benign paroxysmal positional vertigo (BPPV) secondary to sudden deafness (SD) and idiopathic BPPV via retrospective analysis of their clinical characteristics.Methods Seventy-four patients with BPPV secondary to SD and 112 patients with idiopathic BPPV who visited our department from Dec 2019 to Dec 2021 were included in this study. The differences of clinical classification, curative effect, dizziness handicap inventory (DHI) score after treatment and blood homocysteine (Hcy) value before treatment between the secondary group and idiopathic group were observed and compared.Results The rates of BPPV of single semicircular canal in the secondary group and idiopathic group were 33.8% (25/74) and 80.4% (90/112), and the difference was statistically significant (χ²=40.953, P<0.01). The rates of one-time cure in the secondary group and idiopathic group were 50.0% (37/74) and 86.6% (97/112) with a significant difference (χ²=29.467, P<0.01). In the cured cases, the rate of slow phase velocity of nystagmus CP>20% in the secondary group was 67.6% (25/37), which was higher than that of 25.8% (25/97) in the idiopathic group,and the difference was also statistically significant(χ²=20.002, P<0.01). After treatment, the rate of the DHI score ≤ 30 in the secondary group was 31.1% (23/74), which was lower than that in the idiopathic group 73.2%(82/112), the difference was statistically significant (χ²=33.367, P<0.01). Before treatment, the blood Hcy value of the secondary group was significantly different from that of the idiopathic group(t=3.422, P<0.01).Conclusion Compared with the patients of idiopathic BPPV, the incidence of single canal lithiasis is lower with lower one-time cure rate, higher ratio of remnant vestibular function asymmetry and DHI score after cure in those of BPPV secondary to SD due to more extensive, more severe and more lasting damage of vestibule and semicircular canals.