Electromagnetic compatibility is achieved by reducing the interference below the level that disrupts the proper operation of the electronic system or subsystem. This compatibility is generally accomplished by means of electronic filters, and component or equipment shielding. Shielding an electromagnetic field is a complex and sometimes formidable task. The reasons are many, since the effectiveness of any strategy or technique aimed at the reduction of the electromagnetic field levels in a prescribed region depends largely upon the source (s) characteristics, the shield topology, and materials. In this paper, the effect of an incident plane wave with linear polarization on aluminum shield in UHF frequency is investigated, then, the type of shield material is changed and shielding effectiveness caused by it is investigated. Also, the linear polarization of incident wave is converted to circular polarization and shielding effectiveness variation is obtained in this stage. Slots and apertures are very important parameters to determine suitable shielding effectiveness. In following paper, slot is placed on shield, and its shielding effectiveness is evaluated. The effects of slot width variation, slot length variation and slot displacement, on shielding effectiveness are investigated. Finally, the effect of different aperture structure is evaluated and shielding factor is obtained in any stage. The whole of simulations in this paper, are done with CADFEKO.