According to the characteristics of the multi-size structure and the impedance matching theory, a perfect ultra-broadband absorber with a rectangular laminated structure is designed. The absorber is composed of two layers of metal-semiconductor films-semiconductors of different sizes, which can excite multiple resonance modes and achieve perfect absorption of ultra-broadband. The finite difference time domain method is used to study and analyze the absorption spectrum and electromagnetic field energy distribution of the absorber, as well as the influence of polarization angle and incident angle on absorption performance. Numerical results show that the average absorptivity of the absorber is higher than 97% in the range of visible light to middle infrared, and it is independent of arbitrary polarization. When the incidence angle is 60°, the average absorption rate is still higher than 90%. The wide band perfect absorption is achieved by the joint action of gap-surface plasmon polaritons, propagation surface plasmon polaritons and Fabry-Perot resonance.