The present application provides a fusion protein, containing: an anti-CD137 antibody capable of specifically binding to a CD137 molecule or an antigen binding fragment thereof; an anti-CD3 antibody capable of specifically binding to a CD3 molecule or an antigen binding fragment thereof; and a first peptide linker and a second peptide linker. The present application also provides a nucleic acid encoding the fusion protein, an expression vector containing the nucleic acid, a host cell containing the nucleic acid or the expression vector, a method for preparing the fusion protein, a pharmaceutical composition containing the fusion protein, and a use of the fusion protein.