In order to study the degradation mechanism of electromagnetic shielding efficiency of airborne electronic equipment in corrosive environment. The electromagnetic leakage caused by corrosion of filling material of the tiny gap in the aviation chassis was studied. The corrosion sensitive structural parts with conductive rubber and metal gaskets were designed to fill the tiny gap in shielding box. The equivalent model of the tiny gap in shielding box was constructed, and the variation rule of electromagnetic shielding efficiency of equivalent box based on the gasket transfer impedance was studied under different corrosion periods. The effect mechanism of corrosion on electromagnetic shielding efficiency degradation of airborne equipment was studied by means of microscopic analysis. In general, the degradation degree of electromagnetic shielding efficiency of the chassis filled with conductive rubber is better than that of metal gaskets during corrosion, and shielding efficiency of chassis decreases with the increase of frequency in frequency range of 100 ~ 2 GHz. The transfer impedance values of two types of washers increased after corrosion, shielding efficiency of box decreased. With the increase of corrosion time, the change of transfer impedance values of rubber and metal gaskets gradually decreases. After the corrosion test, surface state and impedance characteristics of contact surface of the slot structure of chassis are greatly changed, and the electrical continuity of the contact surface is destroyed. This is the main reason for the increase of electromagnetic leakage of contact surface after corrosion and the decrease of electromagnetic shielding efficiency of chassis.