The effect of metal and magnetic slab on the radiation characteristic of monopole antenna is studied in this paper. The presence of metal slab changes the antenna radiation pattern and it also increases the gain up to 4.6 dB. The radiation characteristic of monopole antenna is determined by the separation distance between planar monopole and metal slab. In addition, magnetic slab also changes the antenna radiation pattern and it also increases the gain up to 3 dB. Metal slab makes antenna generate reflection, but magnetic slab makes antenna generate refraction is their difference. As to the application slab, the initial pattern of the antenna without materials was omnidirectional. However, when the materials were added, its pattern would change, making the antenna to have other usages and transition effect. They will influence electromagnetic in power systems.