The present invention provides a multi-drug-loading site and high drug-loading capacity ligand-drug conjugate. The ligand-drug conjugate has a structure of general formula (I). The ligand-drug conjugate has the characteristics of high loading capacity, high drug efficacy, low toxicity, and low risks. The ligand-drug conjugate can be used particularly to connect to a low toxicity chemical molecule, thereby extending a therapeutic window. Furthermore, the present invention provides an antibody-drug conjugate molecule. The antibody-drug conjugate molecule has the characteristics of multiple drug-loading ability and high drug-loading capacity, such that the antibody-drug conjugate can carry a large amount of a low toxicity chemical molecule and achieve a therapeutic effect without depending on antibody targeting or high toxicity chemicals.[in-line-formulae]TM-{R2-PEG1-[R1-PEG2-(R3-A′-D)n]m}l??(I[/in-line-formulae]