In this work, thorny Au nanoparticles (NPs) a broadband surface plasmon resonance (SPR) peak were used to enhanced the solar thermal conversion (STC) performance. The SPR peak of the thorny Au NPs can be tuned from 562 nm to 812 nm with the size ranging from 42 to 188 nm, which was controlled by the amount of Ag+ in the growth process and the seed additive amount for optical and morphological evolution of Au NPs. Experiments indicated that the thorny Au NPs can greatly enhance the STC efficiency, the maximal increase of which was 152.0% and 18.5% compared with pure water and quasi-spherical Au NPs respectively. Then, the particle heating model was applied to further confirm that the thorny NP can enhance the solar heating process significantly. Results indicated that the thorny Au NP obtained a higher maximum temperature than that of the spherical Au NP owing to a higher heat resource from the solar radiation in the thorns. In addition, a blended nanofluid with different thorny Au NPs showed a highest STC efficiency in all experimental samples that was as high as 85.8% by broadening its absorption spectra. It indicated that tuning the NP morphology or mixing different NPs could be efficient ways to improve the STC performance.