Abstract: OBJECTIVE To study the primary structure of Y-Body^® bispecific antibody based on UPLC-Q-TOF-MS.METHODS Based on Y-Body^® bispecific antibody M808 as the object of study, the relative molecular mass of intact antibody and each subunits before and after deglycosylation, peptide mapping(amino acid sequence) was detected and analyzed by UPLC-Q-TOF-MS and Unify software.RESULTS The relative molecular mass of intact antibody and deglycosylation intact antibody were 128 417.660 5, 125 040.721 0. The relative molecular mass of light chain(LC) and deglycosylation LC were 23 447.232 2, 23 445.560 8. The relative molecular mass of heavy chain(HC) and deglycosylation HC were 50 804.773 2,49 201.605 1. The relative molecular mass of single chain(SC) and deglycosylation SC were 54 189.922 4, 52 415.764 4. The amino acid sequence was basically consistence with theoretical sequence, and the coverage of the complementary determining region attained 100%. N-glycosylation sites located at the Fc of HC and SC, mainly including G1F and G2F.CONCLUSION The primary structure of bispecific antibody can be effectively characterized by UPLC-Q-TOF-MS and Unify software, which provides a basis for ormulation of quality standards.