Glycosylation plays an important role in how the human body functions, including cell recognition, signaling, and immune response. While efforts have been devoted to the analysis of N-glycans, high-throughput quantitative analysis of O-glycans is underexplored. In this study, a multiplexed isobaric labeling method, DiLeuPMP, is introduced. This method combines the release and labeling of O-glycans in one step and achieves accurate MS2-based relative quantification. This method provides an effective and reliable approach for the profiling and high-throughput quantitative analysis of O-glycans in complex samples.