Production of fuel and chemicals from plastic waste is one of the effective ways to upcycle spent plastics, which is an interesting topic and of significance for green and sustainable development. Herein, we demonstrate a highly efficient catalyst, TiO₂ nanoparticle supported Ru nanocatalyst (Ru/TiO₂), for upcycling polyethylene terephthalate (PET) to alkanes in the presence of H₂ and water. Under the optimal conditions (200 °C, 60 bar H₂, and small amount of H₂O), PET could completely convert into alkanes, dominated with cyclohexane and methane. It was indicated that the strong interaction between the TiO₂ support and Ru nanoparticles made electrons flow from the TiO₂ support to the Ru nanoparticles, which thus rendered Ru/TiO₂ to have ability to simultaneously catalyze PET hydrolysis and intermediate hydrogenation. This work realizes the transformation of PET to alkanes, which provides a promising way to chemically upcycle PET.