In recent years，cancer immunotherapy，especially immune checkpoint inhibitor（ICI），has made remarkable progress in clinical practice. However，due to the heterogeneity of immune responses among individuals，patients’responses to treatment vary， making the monitoring of treatment efficacy particularly important. In the tumor microenvironment，the activity of cytotoxic T lymphocyte（CTL）is a key indicator for evaluating the efficacy of immunotherapy. Granzyme B（GzmB），a serine protease mainly present in CTLs，is considered as an important biomarker for early prediction of the response to immunotherapy. Molecular imaging probes targeting GzmB can monitor the changes in GzmB expression at tumor sites during immunotherapy，providing a basis for evaluating treatment efficacy. This review summarizes the research progress of various GzmB-targeted molecular probes，and analyzes the structural design，imaging principle of the probes and their application potential in early monitoring of tumor immunotherapy response，aiming to provide reference for the further development and clinical application of GzmB-targeted molecular probes.