Due to the novel electromagnetic (EM) characteristics of metamaterials, research on metamaterial absorbers (MMAs) drives the field of the absorption of EM waves, and increasing MMAs that realize good absorption in the terahertz (THz) band begin to emerge. However, how to simplify the complex laminations and surface structures of broad-band THz MMAs remains a challenge. In this paper, a terahertz broad-band metamaterial absorber (TBMMA) has been proposed. The TBMMA is designed based on a simple rhombus resonator and its thickness is only 8.5 μm. Also, the period of the unit cell structure p is larger than the average absorption wavelength λ a, which is different from the subwavelength structure of previous MMAs. The TBMMA can achieve an absorptivity over 90% in the band from 5.09 THz to 6.95 THz, and it has characteristics of polarization-insensitivity and wide-angle. The proposed TBMMA can be used in the field of the THz imaging, detection and biosensors. The non-subwavelength structure of the TBMMA also provides a new idea for the design of TBMMAs.