Abstract: Underground water-sealing oil storage in rock cavern is a new oil storage method developed recently. Determination of cavern buried depth is the key in the project and it directly affects project quality, safety and costs. Based on a project in Zhanjiang City, a complete process is discussed to determine buried depth of the rock cavern. The rock cavern top burial depth is preliminarily determined based on water sealing conditions and rock quality and then Flac3D calculation software is used to analyze the area of underground water-sealing oil storage in rock cavern in Zhanjiang City. Numerical simulation study is carried out on the mechanical behavior characteristics of surrounding rocks in the two groups of caverns subject to full face excavation by modeling and boundary conditions to determine the more appropriate buried depth of the rock cavern. Finally, buried depth simulation results are compared and optimized from the aspect of project costs in order to determine the optimal buried depth of the water-sealing oil storage in rock caverns. As shown from the project application results, the method is of certain practicality and can provide a useful reference to the other similar projects in the future.