A simple design of broadband metamaterial absorber (MA) is numerically inves- tigated at terahertz frequencies in this paper. The unit cell of this absorber consists of two square rings with different geometric dimensions, a dielectric substrate and continuous metal film. A wide frequency band ranging from 2.95 THz to 3.71 THz with absorption rate of over 90% is obtained. Distributions of surface current density on the front and back metallic lay- ers are illustrated. Finally, the loss contributions of metallic structures and dielectric substrate are also discussed. The proposed absorber is an ideal candidate as absorbing elements in many applications, such as thermal detectors, terahertz imaging, and stealth technology.