In this study, a terahertz absorber based on graphic graphene, which exhibited tunable ultra-wideband absorption characteristics, was designed. The top, middle, and bottom of the absorber comprised ultra-thin graphene, dielectric, and gold layers, respectively. The absorber was designed and simulated by changing the thickness of the middle layer and the Fermi energy level of the top layer; the Fermi level of graphene could be controlled by changing the gate voltage. The results show that the absorber exhibits ultra-wide frequency absorption in the low-frequency region, and the absorption characteristics are optimized when the thickness of the middle layer is 30 μm; the opening and closing of the absorber can be controlled by changing the Fermi energy level of graphene, while the frequency position and bandwidth of the absorption peak are adjusted to make the absorption peak move close to 431 GHz, thus realizing a tunable function of the absorber. When the Fermi energy level of graphene is 0.4 eV, the bandwidth with an absorption rate of more than 90% is 1.8744 THz and the peak absorption rate is 99.3357%. The absorber achieves perfect absorption.