For the reduction of electromagnetic biological effects from cellular phones, the electrical field radiation from cellular phone antenna is reduced by using partial ferrite material added on the phone case as ground plane. On the given properties (permittivity, permeability and conductivity) of ferrite material, the characteristics of monopole antenna is analysed depending on the variation of ferrite added configuration(thickness and shape). According to this analysis, the design method and direction to minimize the biological effects to human head is proposed in 1.7 GHz band PCS phones. For the exact analysis involving the permittivity, per-meability and conductivity of ferrite material, FDTD numerical method is used.