Abstract: The lightning discharge process is accompanied by electromagnetic effects, thermal effects, and mechanical effects, while it can generate lightning electromagnetic impulse(LEMP), causing severe damage to electrical and electronic equipment in buildings. In order to protect the equipment from electromagnetic radiation damage caused by LEMP, most buildings are taking corresponding LEMP protection measures. Lightning current injection method and space radiation method are often employed to measure the attenuation of magnetic shielding. In this paper, we analyze the difference between these two methods in measuring buingding structures(such as walls, gridded shield net, etc.) attenuation effects against magnetic field cauesd by LEMP. In addition, we introduce the principles of the spatial radiation method. As a result, the capacities of inspection and testing of lightning protection system in building has been elevated to a new level.