Abstract: In order to make the designed hole spacing to ensure the stability of surrounding rock, the security of construction and operation and the economic rationality, the Geological Strength Index (GSI) proposed by Hoek and Brown and the empirical formulas of Hoek-Brown are adopted to determine the mechanical parameters of rock mass. Taking the oil storage cavern of an underground water-sealed oil storage project in Liaoning as an example, numerical analysis is conducted for the surrounding rock spacing with FLAC3D software, displacement criterion is used to explain the analysis results, and then the rationality of the cavern spacing is judged. Finally, it is pointed that the program with 60 m spacing can realize required stability and safety of the overall project and it has a certain guiding significance for engineering practice.