We present a metamaterial absorber (MA) composed of double layers of metal dendritic cells,dielectric substrate and metal film.With three different sizes of dendritic cells arranging in hexagonal array,it is able to find three discrete absorption peaks.Our experiments confirm that,if the frequencies of the three absorption peaks go closer,a combined broadband absorption peak could be achieved.Compared with the metamaterial absorber with only one singer layer of metal dendritic cells,the double-layered metal dendritic cells adopted in our MA greatly improve the absorption efficiency.The experimental result shows an absorption band of 1.93 GHz width with the absorptivity higher than 90% in the frequency range between 9.79 and 11.72 GHz.The proposed MA has a series of advantages such as high absorptivity,simple structure,small thickness,2D isotropy and wide absorption band.