Abstract: The photothermal conversion film is the core component of solar photothermal utilization and directly affects the conversion efficiency of the entire system. A Ti/a-C:H/Ti（H）/a-C:H/Ti（L）/a-C:H composite photothermal conversion film was prepared by reactive magnetron sputtering using Ti and graphite targets. The morphology characteristics and structural composition of the film were studied and discussed, and its optical absorption properties were analyzed. The results show that the composite film has significant spectral selectivity, with Ti and C existing in the absorption layer in the form of TiC. Meanwhile, the high surface roughness of the film helps enhance its light absorption ability, with an absorption rate of 0.91 and an emissivity of 0.13, demonstrating excellent optical performance.