This chapter explores the microseismic monitoring and stability analysis of large underground water-sealed petroleum caverns. It highlights the background and significance of the study, reviews the research progress both domestically and internationally, and analyzes numerical methods, safety monitoring techniques, and microseismic monitoring approaches for these structures. Key challenges in current research are identified. Using Jinzhou underground water-sealed oil caverns as a case study, the chapter examines regional geological and hydrological conditions, the establishment of a microseismic monitoring system, and the accuracy of microseismic location and signals. The spatial and temporal distribution of microseismic activity and the local stability of surrounding rock are assessed. Additionally, numerical simulation based on the Complex Distinct Element Method (CDEM) is conducted, incorporating the project’s profile, the method’s principles, and simulation results. Comparative analysis between numerical findings and microseismic monitoring data further reveals insights into the stability and safety of underground caverns. This comprehensive study offers valuable theoretical and practical support for the design, monitoring, and maintenance of underground water-sealed petroleum storage systems.