复杂工程细缝为金属腔电磁屏蔽效能的评估带来了挑战。采用时域有限差分(FDTD)法结合环路(CP)法，在不改变原有粗网格剖分的基础上，实现了对三维复杂细缝结构金属腔电磁屏蔽效能的快速计算。提出复杂工程细缝的等效模型，提高了复杂细缝结构的CP编程和计算效率，计算结果与采用精细网格剖分的传统FDTD(fine-FDTD)计算结果吻合很好，验证了等效模型的有效性。在此基础上，分析了两种开有典型工程细缝金属腔在0~3 GHz内的电磁屏蔽效能，计算结果与fine-FDTD算法结果吻合很好，且计算效率大大提高。

Thin slots with complex configurations used in practical engineering make the evaluation of electromagnetic shielding effectiveness(SE) for metallic enclosure increasingly challenging. The contour path (CP) method is adopted to deal with the complex thin slots in order to keep the coarse gridding in FDTD programming. An equivalent model with simple configuration is presented to replace the complex nested slits, and as a result, the programming and calculation efficiency of the CP-FDTD method is improved when dealing with thin slots with complex configurations. The equivalent model and CP-FDTD are used to calculate the SE of metallic enclosure with two typical kinds of thin slot configurations at the wide frequency range respectively. Results are in good agreements with those obtained by using fine-gridded FDTD, and high calculation efficiency is achieved at the same time.