Abstract: In order to meet the design requirements of multi layer absorbing materials, such as thin in thickness, light in weight, and broad in absorbing band, an effective optimization is needed to carry on preliminarily. Based on the experimental data of electromagnetic parameters of each layer, an object function is constructed appropriately, and then applying the numerical method one can optimize the radar absorbing property of the whole composite. Hence the effectivity of material research is improved. Under the optimizing method, A radar absorbing material is developed, which has a nice property reflectivity below -10dB within band from 8 to 18GHz.