Objective Retrospective analysis the clinical characteristics of BPPV secondary to sudden deafness(SD) and primary BPPV, Compare their efficacy and outcomes, and analyze the possible causes. Method Observe 74 patients with BPPV secondary to SD who visited our department from December 2019 to December 2021,compare with 112 patients with primary BPPV admitted to our department in the same period. To observe and compare the difference of clinical classification, curative effect, HDI score after treatment and blood homocysteine value before treatment between patients with sudden deafness secondary BPPV and patients with primary BPPV. Result In secondary group, BPPV of single semicircular canal are 25 cases(33.8%),and 90cases(80.4%) in primary group. There is a significant difference between the two(x2=40.953 P<0.01). In secondary group, patients of once cured are 37 cases(50.0%),and 97 cases(86.6%) in primary group. There is a significant difference between the two(x2=29.467 P<0.01). There were 25 cases (67.6%) with CP>20% in the secondary group after one cure, which was higher than 25 cases (25.8%) in the primary group. There was a significant difference between the two groups（x2=20.002 P<0.01). After treatment, the DHI score in the secondary group was ≤ 30 in 23 cases (31.1%), which was lower than that in the primary group in 82 cases (73.2%). There was a significant difference between the two groups (x2=33.367 P<0.01). Before treatment, the blood homocysteine value of the secondary group was significantly different from that of the primary group(t=3.422 P<0.01). Conclusion In secondary group,the incidence of single tube lithiasis is lower,the one cure rate is lower,the ratio of left vestibular function asymmetry after cure is higher,compared with primary group.The reasons are as follows，the damage range of vestibular and semicircular canals of BPPV secondary to SD is more extensive, more severe and more lasting.