Abstract: A bispecific antibody, which specifically binds the surface antigen CD3 of immune cells and the BCMA antigen on the surface of tumor cells and which may bind to human CD3 with high affinity, induce T cell proliferation, and mediate tumor cell killing effects. The bispecific antibody may be used to mediate the T cell-specific killing of target cells in in vitro tests. The method for constructing a bispecific antibody is simple, and avoids the possibility of mismatching between two sets of light chains and heavy chains of a heterologous bispecific antibody, thus the difficulty of antibody purification is reduced, the affinity of the obtained antibody is high, the side effects of induced cytokines are few, and safety is high.