Abstract: This paper used size exclusion chromatography and analytical ultracentrifugation techniques to perform orthogonal analysis of the molecular size variants of ZG154 and ZG187 antibodies. Moreover, liquid chromatography-mass spectrometry, circular dichroism spectroscopy, dynamic light scattering and differential scanning fluorescence techniques were used to systematically analyze the factors causing aggregation and fragmentation. The results showed a 30.7% increase in the deamidation modification at the 329 site of asparagine in the ZG154 sample when stored at 40 ℃. The related modifications did not alter the secondary and tertiary structures, as well as the stability of the protein, but accelerated aggregation by increasing intermolecular interactions and led to fragmentation due to the production of succinimide. Moreover, there was a 36.9% increase in the oxidative modification at the lysine 430 site in the ZG187 sample when stored at 40 ℃, which reduced the stability of the protein and led to fragmentation. However, it did not change the secondary and tertiary structures of the protein, and the molecules always exhibited mutually exclusive interactions, thus not leading to aggregation. Furthermore, the changes in the sedimentation coefficient of ZG154 dimer and the non-covalent interactions between ZG187 molecular fragments were revealed through analytical ultracentrifugation sedimentation velocity analysis. These results describe suitable detection methods which can be combined to resolve the aggregation and fragmentation problems in the development and production of the above-mentioned drugs.