Objective To investigate the clinical features of primary autoimmune cerebellar ataxia （PACA）， and to provide experience for the diagnosis and treatment of this disease.Methods Related data were collected from the patients with PACA who were admitted to The Third Xiangya Hospital of Central South University from January 2018 to January 2023， and a retrospective analysis was performed for their clinical manifestations， laboratory examination， and radiological examination.Results A total of six patients were enrolled， among whom there were three male patients and three female patients， with a median age of 54 years. All six patients had acute or subacute onset with ataxia as the main symptom， and there was no history of prodromal infection. Basically normal results were obtained from routine cerebrospinal fluid test， biochemical examination， cytology， and cranial magnetic resonance imaging （MRI）. All patients tested negative for autoimmune cerebellar ataxia antibody in cerebrospinal fluid and paraneoplastic syndrome antibody in blood. Four patients were found to have abnormal indicators associated with connective tissue disease. Of all six patients， four received immunoglobulin therapy， among whom 2 received hormone therapy and 1 received hormone and cyclophosphamide. After treatment， all six patients had varying degrees of improvement in ataxia， and the patients receiving immunotherapy or hormone therapy had significant relief of symptoms.Conclusions PACA is an immune-mediated disease with no clear etiology or specific neuronal antibody. Ataxia is the main clinical manifestation， and cerebrospinal fluid test and radiological examination often have basically normal results. Immunotherapy is effective in most patients.