Abstract: In this paper, the idea of equivalent is used to research the gas leakage characteristics of shielding box sealing structure of high-power radial line spiral array antenna. Firstly expounding the method of equivalent area, then combined with the actual situation and the related formulas to obtain the equivalent area of sealing structure. On this basis, the gas leakage process of sealing structure has carried on the theoretical calculation and numerical simulation, and the complete gas leak test is verified. Research calculation, the numerical simulation is more accurate with the faster, more cost savings and distribution characteristics of gas parameters can be achieved. The method provides the means for rapid implementation the gas leakage characteristics analysis of antenna sealing structure.