A tunable broadband, polarization insensitive and incident angle insensitive metamaterial terahertz absorber is proposed, which consists of silicon semi-ellipsoid/semi-spherical structure, graphene, dielectric layer and metal back plate. Based on the known results, the electric field results under different chemical potentials of graphene and different structural conditions were analyzed by simulation under the condition of vertical incident TE wave show that under the synergism of continuous and multimode Fabry-Perot resonances formed by silicon semi-ellipsoid/semi-spherical subwavelength structure and multiple discrete plasma resonances excited by graphene the absorption spectrum is smoothed and expanded so that the structure can achieve a wide range of adjustable absorptivity and a broadband absorption characteristic of nearly 100% absorptivity. When the chemical potential of graphene is around 0.2 eV and 0.9 eV, it can obtain about 5.7 THz and 7 THz wideband terahertz wave absorption (the absorption rate is more than 90%), respectively, and its maximum absorption rate is close to perfect absorption (about 99.8%). In addition, the structure is insensitive to 360° polarization and incident angle higher than 60°. In the above angle range, the absorptivity of the absorber can still be maintained to more than 90%. and the structure has potential applications in terahertz wave detection, spectral imaging and stealth technology.