Abstract: Chemotherapy is the main method of pre-tumor treatment, yet chemical drugs also kill normal cells while killing tumor cells. Antibody-drug conjugates (ADCs) were produced in order to ensure the precise action of chemical drugs on the lesion site. Traditional ADCs, which are conjugated using lysine residues of antibodies or sulfhydryl groups obtained by reducing the disulfide bond of antibodies, have the disadvantages of poor homogeneity and low stability. Highly homogeneous ADCs can be obtained using site-specific conjugation techniques to ensure reproducibility between batches in the manufacturing process. This paper reviews several site-specific conjugation techniques for ADCs.