Patients with bipolar disorder （BD） exhibit persistent cognitive impairment， which has adverse effects on the course and prognosis of the disease. Brain-derived neurotrophic factor （BDNF） is a type of neurotrophic factor in the family of nerve growth factors， which is involved in the genesis， survival， and synaptic plasticity of neurons， and is closely related to cognitive impairment in BD patients. This paper reviews the relationship between BDNF expression levels， gene polymorphisms， and cognitive impairment in BD， as well as the study of BDNF epigenetics， BD and cognitive impairment， aiming to provide a theoretical basis for early identification and treatment of cognitive impairment in BD patients.