This paper proposes an ultra-broadband absorber operating in the terahertz band, utilizing the surface plasmon resonance characteristics of micron-scale structured Dirac semimetals and single-layer graphene and the bound-state electromagnetic coupling effect in the continuum domain. The performance of the absorber was verified by finite difference method simulation. Its average absorption rate reached 92% in the range of 38.64 to 227.76 THz. Where 43.44-50.4 THz, 62.48-72.96 THz, 85.68-87.12 THz and 192.24-195.36 THz band with an average absorption rate of 99%. The study also explored the Fermi level and relaxation time of graphene and found that the absorber has good physical tunability. The absorber has a structural symmetry, independent of the polarization. Compared with previous designs, the absorber designed in this paper has a simple structure, is easy to adjust, is insensitive to large angles, and has extensive application potential in solar energy, photoelectric detection, sensors and other fields.