The existing analysis method of the seam hole cavity has poor precision

thus we propose a hybrid method for computing the shielding effectiveness（SE） of a cavity with apertures more accurately

based on the mode matching method and the electromagnetic topology theory.The proposed method can quickly and accurately calculate the SE with arbitrary incident and polarized plane wave

and the SE of a cavity with single or double apertures at arbitrary position.According to the pattern matching method

the cavity aperture is equivalent to the discontinuous waveguide boundary

and the scattering matrix of the hole is obtained by solving the coupling coefficient.Then the cavity with aperture will be analyzed by a method of electromagnetic topology

and a propagation relation equation and a scattering relation equation are obtained.At last

the voltage value at a

ny point in the cavity can be obtained

and the shielding effectiveness of the cavity is obtained.By comparing the theoretical results with the CST simulation results

it is shown that the hybrid method is superior to the Robinson equivalent circuit method and has advantages over the CST in running time and memory resource in the range of 0

2

GHz.