As a method of effectively harnessing solar energy resources, the absorption efficiency of solar absorbers is of paramount importance in optimizing energy use. We propose an ultra-broadband solar absorber that utilizes a multi-resonant cavity nanopillar disc structure incorporating V2O5 and TiN. The absorption properties of the absorber are determined by the finite-difference time-domain simulation method. The results indicate an absorbance of over 90% across the entire spectral range of 300 to 2500 nm and a perfect absorption of over 99% from 540 to 2290 nm. In addition, the absorber is polarization-independent and angle-insensitive with the average absorbance above 90% even at a 60-deg incidence angle. The broadband absorption is mainly achieved by the synergistic effects of surface plasmon excitation, localized surface plasmon resonance, and multi-resonant cavity structure. The photothermal conversion efficiency of the absorber is 95.9% at 800 K. The proposed solar absorber has potential applicability in thermal photovoltaic devices and solar energy harvesting.