In this paper Transmission Line Matrix Method (TLM) is applied to model the Shielding Enclosure of Wireless Portable Digital Device (operating band 2.40 – 2.48 GHz) which is made up of Frequency Selective Surface (FSS). The FSS is madeup of Jerusalem cross etched from the conductor sheet. The main objective of the enclosure design is to provide high transmittance in the required wireless band and provides high shielding outside the band. The important factor influencing the performance of the FSS is the polarization. The influence of polarization on Shielding Effectiveness of the enclosure is calculated. This approach can be used to design Shielding Enclosure, used for equipments. TLM method is used since, among the numerical methods available its best suitable time domain method for EMC application which consume very less computation time. © Research India Publications.