In the present study, a metamaterial solar absorber with ultra-wideband and high absorption is designed based on the characteristics of combined resonant structure and impedance matching theory. The absorber unit cell is composed of a cross-shaped and metal/dielectric/metal stack structure, and the combined resonant structure effectively expands the absorption bandwidth. The finite difference time domain method is used to analyse the absorption characteristics, and numerical results reveal that the absorber has an average absorptivity of 94.9% in the 300-4000 nm band with an absorption bandwidth of 3700 nm, which can effectively cover the visible and infrared regions. The absorber exhibits certain polarisation-independent characteristics over the entire absorption band range and maintains an average absorption of 93% at a large angle of 60° oblique incidence. It can be seen from the electromagnetic field distribution at the resonance wavelength, that the broadband and high-absorption characteristics of the absorber are mainly derived from Fabry-Perot resonance, slow-wave effect, surface plasmon resonance, localised surface plasmon resonance, and hybridisation coupling between multiple resonances. Whereas, with the development of nano-processing technology, other similar metamaterial absorber structures have also been manufactured for the test, which also provides the basis for the fabrication of the proposed absorber structure. This work provides a reference value for the design of invisible equipment and solar cells and provides new ideas for the high-efficiency absorption of solar energy.