In this paper, a novel metamaterial absorber is proposed. The absorber is based on metamaterial which is a kind of artificial periodic structures. The top layer of the absorber is composed of split ring resonators (SRRs) with a square metal patches (SMPs) in each SRR and its bottom layer is covered with whole metal. The special structure of the top layer makes the unit cell resonate at adjacent frequencies in different modes which makes the absorber work in broadband. Moreover, the oblique and symmetrical unit cell makes the absorber suitable for both TE and TM wave, namely it is polarization-insensitive. Simulation and calculation results show that the absorber is able to absorb more than 75% of the EM power from 9.6 to 18.45 GHz with a relative bandwidth of 63.10% for both TE and TM wave. The proposed absorber is also fabricated and measured. The experimental results agree with the simulation ones very well. The broadband and polarization-insensitivity properties of the proposed absorber make it have a promising application prospect in shielding and stealth technology.