Abstract: Objective: To observe the characteristics of positional nystagmus and clinical profile of patients with positive positional test, and to explore its possible pathogenesis. Method: One hundred and twenty-one patients with positive positional test in the vestibular function examination were enrolled in the Peking University International Hospital from January to June in 2017. According to the 2017 BPPV guidelines, patients with test positive positional nystagmus were divided into two groups:definite BPPV and the controversial syndrome. Analyses of gender, age and characteristics of nystagmus, with or without recurrent dizziness, headache, and motion sickness were undertaken between the two groups, as well as response to the repositioning maneuver. Result: Of the total 121 cases, 49 cases were diagnosed as definite BPPV, accounting for 40.5%, 72 cases as controversial syndrome, accounting for 59.5%. The proportion of women in the two group was 76.2% and 78.9%, respectively. The average age of definite BPPV and the controversial syndrome was 51.2±16.8 and 51.3±15.7, respectively. There were significant differences in nystagmus duration, spontaneous nystagmus and nystagmus after head-shaking between the two groups by chi square test(P<0.01). The mean intensity of horizontal and vertical nystagmus in posterior semicircular canal BPPV was(10.2±7.4) °/s and(36.6±17.5) °/respectively. And the mean intensity of nystagmus in the strong and weak side in horizontal semicircular canal BPPV was(40.8±25.1) °/s and(20.7±11.1) °/respectively. The intensity of horizontal and vertical nystagmus of the controversial syndrome group was(7.2±7.7) °/s and(7.2±4.3) °/s respectively. The incidence of headache in the controversial syndrome group was significantly higher than that in the BPPV group, P=0.013. According to the guidelines, patients were evaluated one day after the initial treatment. The cure rate and effective rate of the definite BPPV group was 75%(36/48) and 87.5%(42/48), and was 0 and 30.4% in the controversial syndrome group respectively. Conclusion: The patients in controversial syndrome group have a preponderance of exhibiting positive nystagmus during positional test. Nystagmus were usually of low velocity and sustained. Most of these cases presented spontaneous nystagmus and headshaking induced nystagmus, as well as headache and lacunar infarctions in history, and the response to the repositioning maneuver were often poor. It may be related to vestibular migraine and central nervous system. The diagnosis of BPPV must be prudent. Both characteristics of nystagmus and medical history should be carefully analyzed to avoid overdiagnosis.