Synthesis of atomically dispersed catalysts with high metal loading and thermal stability is challenging but particularly valuable for industrial application in heterogeneous catalysis.Here,we report a facile synthesis of a thermally stable atomically dispersed Ir/α-MoC catalyst with metal loading as high as 4 wt％,an unusually high value for carbide supported metal catalysts.The strong interaction between Ir and the α-MoC substrate enables high dispersion of Ir on the α-MoC surface,and modulates the electronic structure of the supported Ir species.Using quinoline hydrogenation as a model reaction,we demonstrate that this atomically dispersed Ir/α-MoC catalyst exhibits remarkable reactivity,selectivity and stability,for which the presence of high-density isolated Ir atoms is the key to achieving high metal-normalized activity and mass-specific activity.We also show that the water-promoted quinoline hydrogenation mechanism is preferred over the Ir/α-MoC,and contributes to high selectivity towards 1,2,3,4-tetrahydroquinoline.The present work demonstrates a new strategy in constructing a high-loading atomically dispersed catalyst for the hydrogenation reaction.