In recent years, the biopharmaceutical industry has grown rapidly, and the market size of monoclonal antibody drugs has increased significantly. Accurate structural characterization and quality control are the supporting technologies for the development of monoclonal antibody drugs. As a significant post-translational modification of antibody drugs, glycosylation has an important influence on its efficacy, stability, and immunogenicity. The existing literature usually uses liquid chromatography-mass spectrometry to perform major glycosylation modifications of monoclonal antibody drugs. Characterization, there are few studies on low-abundance glycosylation, but the characterization and control of low-abundance glycosylation cannot be ignored. In this study, we have established a qualitative and quantitative analysis technology for N-glycans based on RapiFluor-MS reagent-labeled monoclonal antibody drugs. This method has a short sample processing time and high sensitivity. It can not only characterize the main glycoforms of three monoclonal antibody drugs (adalimumab, bevacizumab, and trastuzumab) but also can quantify low-abundance N-glycans. The results of the study showed that the main glycoforms specified in the Pharmacopoeia could be detected in different batches of monoclonal antibody drugs, but the content of N-glycans in different batches of samples is not identical. After that, we analyzed the N-glycans connection sites and glycoforms at the intact glycopeptide level, further enriching the N-glycans structure information of the monoclonal antibody. The qualitative and quantitative analysis technology of N-glycans based on RapiFluor-MS reagent-labeled monoclonal antibody drugs can realize the in-depth characterization and control of glycosylation modification of monoclonal antibody drugs.