Disclosed herein is a bi-specific antibody that specifically directs a therapeutic agent to a cancer cell by targeting a tumor antigen of the cancer cell, and thereby suppresses the growth of the cancer or blocking the invasion or metastasis of the cancer. The bi-specific antibody of the present disclosure includes a first antigen binding site that binds to polyethylene glycol (PEG); and a second antigen binding site that binds to a target ligand, such as a tumor antigen.