Solar photo-thermal conversion is the simplest way to utilize solar energy by using nanofluid as the working medium. In this paper, we aim to investigate the broadband optical absorption and high-performance photo thermal conversion via CuS nanofluids to realize the efficient solar energy utilization. Nanostructured CuS nanospheres and nanotubes were successfully synthesized by using simple hydrothermal reaction. The crystal structures, element compositions and surface properties of the obtained Cull nanostructures were characterized. And the formation mechanisms of the nanostructured CuS were discussed. The optical absorption and photo thermal conversion performances of the CuS nanofluids based on water were studied. The UV/Vis/NIR absorption spectra tests show that the CuS nanofluids prepared have strong optical absorption in both visible light and near infrared light regions. The photo-thermal conversion results indicate that the CuS nanofluids possess good photo-thermal conversion performances, and the maximum temperature of the nanofluid reaches about 72.15 degrees C only with the volume fraction of 0.02% related to the nanotube nanofluid. Moreover, at the same volume fractions, the nanotube nanofluids show better photo-thermal conversion performances than those of the nanosphere nanofluids. This implies a simple approach to enhance photo-thermal conversion for efficient solar energy utilization.