The present disclosure relates to a bispecific antibody that specifically binds to alpha-synuclein and IGF1R, and an use of the bispecific antibody for the prevention, treatment and/or diagnosis of synucleinopathies associated with alpha-synuclein or alpha-synuclein aggregates, and can allow the alpha-synuclein antibody or an antigen-binding fragment thereof to penetrate the blood brain barrier to exert its action in the brain, and extend the half-life to maintain the efficacy for a long time.