Abstract: The high ground stress of deep underground cavern has a great influence on its stability, the stability and endurance of a cavern is quite important for the sealing of the oil products stored in it, and its stability is crucial to the success of the whole project. In this paper, one real underground water-sealed oil storage project in Liaoning was taken as an example. Its stability was numerically analyzed by FLAC3D. The stability of the oil storage cavern in the actual working condition of excavation was analyzed. In addition, the stability of the cavern with and without support was analyzed from the aspects of surrounding rock stress and displacement deformation. It is shown that the surrounding rocks of the oil storage cavern don't exceed the compression strength of the rock and the size and region of the tensile stress satisfy the requirements. By virtue of simulation analysis, the weak positions of the cavern in the process of excavation are identified. It is suggested to strengthen the support and monitoring & measuring on these weak points during design and construction. The research results provide the theoretical basis for the studies on the stability of oil storage caverns of large-section underground water-sealed oil storages.