为研究入射电磁波与缝隙参量对矩形腔体屏蔽效能的影响，提出基于透射定律结合等效传输线方法对腔体的电磁屏蔽特性进行分析。详细推导了经缝隙透射进腔体内的电场，将透射电场作为等效电压源并对传统的传输线模型进行了修正，使之能计算任意方位入射的电磁波及缝隙偏离体壁中心时的情况；并对此方法的计算公式进行了扩展，使其能分析不同形状、孔阵、孔距及损耗等参量对腔体屏蔽效能的影响。研究表明：缝隙位于体壁中心时的屏蔽效能比靠近体壁边沿时差；相对入射角和方位角而言，极化角对腔体的屏蔽效能影响较大；在保持孔阵总面积不变的情况下，通过减小孔径来增加孔的数目或增大孔间距都可提高腔体的屏蔽效能；屏蔽体内损耗因子越大，则对腔体内的谐振频率抑制效果越明显。通过与腔体内谐振频率理论值、数值方法结果的比对分析表明，修正和扩展的解析方法结果可信，且利于各参量对腔体屏蔽效能的分析，适用范围更广。

In order to study the influences of the incident electromagnetic wave and seam parameter on the rectangular cavity of shielding effectiveness (SE), SE analysis of cavity based on the transmission law combined with equivalent transmission line method was performed. The transmission into cavity of electric field was derived in detail, we took the transmission electric field as equivalent voltage source and revised the traditional transmission line model, and the calculation formula of this method was extended, it could analyze different shapes, hole array, hole spacing and loss, etc. Research shows that hole located in the center of the body wall of SE was worse than that near the body wall edge area. Compared with incident angle and azimuth angle, polarization angle has greater impact on the cavity SE. When keeping hole array area unchanged, decreasing aperture diameter, which increases the number of holes and hole spacing, can improve the cavity SE. Greater loss factor of cavity can induce better resonant frequency suppression effect. By analysis of cavity resonance frequency with theoretical and numerical methods, the result obtained by modification and expansion of the analysis method is credible.