Proteolysis, an irreversible post-translational modification catalyzed by proteases, plays a crucial role in various biological processes. Exploring abnormally hydrolyzed proteins in pathological tissues is a valuable approach for elucidating the mechanisms underlying disease development. Herein, we have developed a cleavable 2-pyridinecarboxyaldehyde probe (2PCA-Probe) that enables efficient and in-depth N-terminomics detection, addressing limitations of previous methods. Furthermore, we unexpectedly discovered a new marker capable of identifying N-terminal chemical labeling with the 2PCA-Probe and elucidated the reaction mechanism. Using this probe, we identified 4686 N-terminal peptides in colorectal cancer and adjacent tissues, significantly expanding the depth of the N-terminome and revealing the potential role of abnormal protein hydrolysis in colorectal cancer development.