In this study, atomically dispersed metal catalysts supported on metal oxides are prepared through a ball milling method. The Ru-1/NiO catalyst shows superior performance for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF), with 91.1% HMF conversion and 81.3% selectivity to DFF under 110 degrees C for 2.0 h. It also displays promising recyclability with no aggregation after three catalytic runs. Moreover, the ball milling method shows greatly favorable applicability in preparing a family of oxide-supported atomically dispersed noble-metal catalysts. Our approach not only provides a facile, low-cost, and green method to atomically dispersed catalysts but also benefits the development of highly efficient catalysts for biomass conversion reactions.