With the development of communication technology,adaptive optical abs orber with broadband and high response band has become the focus of attentions and research at home and a broad.A communication band electromagnetic metamaterial absorber is designed based on three-grating c ascade structure of different material and size.The influence of structural design parameters on absorption s pectrum is numerically analyzed by FDTD,and the optimal structure is obtained.The simulation results show that the absorption spectrum based on surface plasmon resonance and FP cavity resonance is mainly concentrated in t he communication band of 0.66~1.78μm,and the absorption rate is above 94%.The bandwidth of ultra-high absorption spectrum is obviously broadened with the increase in the thickness of the dielectric layer. The three-grating width ratio and height ratio has no effect on the absorption bandwidth,but has a great effect o n the absorption rate.Because FP cavity mode and SPP mode,these two resonance mechanisms are in the same cell cy cle,the resonance wavelength along the opposite direction of the drift,almost cancels each other. As a result,the absorption spectrum bandwidth is not sensitive to the period.The absorber has the advantag es of simple structure,small size,easily integration with chip,adjustable absorption wavelength,wide bandw idth and insensitive to incident angle of light source.It has potential application in the fields of broadband o ptical communication,photovoltaic power generation and optical detection.