Based on the electromagnetic resonant characteristic of the metallic dendritic cells, we present a metamaterial absorber (MA) composed of periodic array of double dendritic cells. The unit cell of the absorber is composed of two metallic elements on the substrate, a two-level dendritic cell and a three-level dendritic cell are located on each side separately. Designing different impedance matching conditions, the effect of impedance matching on the absorptivity is found. The experimental results show that a maximum absorptivity of 90% can only occur when the MA layer is impedance-matched to free space. At the same time, increasing the number of MA layers can effectively enhance the absorptivity. For 3 layers, the absorptivity above 99% can be obtained, that is to say, a perfect MA is realized in the engineering sense.