Provided are an anti-PD-L1/anti-4-lBB natural antibody structure-like heterodimeric form bispecific antibody and a preparation thereof. Specifically, provided are an anti-PD-L1/anti-4-1BB bispecific antibody that has natural IgG features, that has no mismatch between heavy and light chains and that is in the form of a highly stable heterodimer, as well as a preparation method therefor. The bispecific antibody can simultaneously bind two target molecules and is more effective in treating complex diseases and has fewer side effects.