Abstract: It is proposed a absorbing device composed of two metallic plates with periodical slits and groove.The interaction between metal and electromagnetic wave is simulated by use of Finite Difference of Time Domain.It is found that there two absorbing peaks in considered frequency range,is which change differently with structure parameter,such as the period and width of slit,the space between two metallic plate and the depth of grooves in second plate.Combining with near fields,it is believed that surface plasma on the surface of first plate excited by slits couple wave into structure,then the produce surface plasma resonance and F-P resonances,leading to different wavelength wave being absorbed through damping oscillations.