In order to solve the problem of oil leakage at the bolted connection of the combustion chamber casing flange, this paper derives the deflection deformation equation of the bolted connection structure by using the analytical method based on the cantilever beam deflection and deformation theory, and establishes a method to optimize the sealing design of the connection structure; the fine finite element of the casing bolted connection is established in ANSYS to calculates the axial clearance of the flange joint surface under different load forms, and the implementation plan to strengthen the sealing performance of the connection is also proposed. Through numerical simulation, the sealing effect of the sealing ring of different thicknesses is clarified, which is to improve the bolt connection of the casing flange, and to provide a reference for oil leakage.