Abstract: Antibody-drug conjugates(ADCs), as an emerging therapy for cancer treatment, have made significant progress in the past few decades. However, due to the heterogeneity of ADCs, they still face various issues and challenges in clinical therapy. Therefore, site-specific conjugation techniques have become a crucial area of research in ADCs, and in recent years, this field has witnessed numerous breakthrough advancements, empowering ADCs with enhanced performance. The review provides a comprehensive overview of the frontiers in site-specific conjugation technologies for ADCs. Categorized into seven major classes including lysine-based, cysteine-based, low-abundance amino acid-based and glycosylation site-based conjugation techniques, ribosomal incorporation of unnatural and noncanonical amino acids and enzyme-mediated conjugation techniques, it meticulously describes 21 classical and emerging techniques such as the THIOMAB technology and linchpin-directed modification, in order to offer valuable insights for the development of next-generation ADCs.