While supported-noble-metal catalysts have been widely investigated in hydrotreating reactions, a crucial issue that the catalytic system is still confronted with is developing an efficient approach to gain the high dispersion of noble metals under reducing conditions. In this work, Ru was supported on two MnO_x with different specific surface areas (SSAs), and a much higher dispersion of Ru (83%, in contrast to 42% of the other one) was surprisingly observed over MnO with much lower SSA (around one-third of the other one). A suite of complementary characterizations demonstrates that, compared with the catalyst with high SSA (Ru/MnO-H), the MnO in the one with lower SSA (Ru/MnO-L) contains enriched surface oxygen that creates more abundant sites and bears stronger strength to anchor Ru species, mitigating the aggregation of Ru under reducing condition. This not only enriched active sites (i.e., exposed Ru), but also created a more electron-deficient Ru domain and thus enhanced the redox property of the surface, leading to the lower barrier for C–O bond hydrogenolysis. In the hydrogenolysis of diphenyl ether, Ru/MnO-L exhibited significantly enhanced activity (i.e., 6 folds of Ru/MnO-H) and high stability. This work provides an approach to regulate the surface chemistry of support for the high dispersion of supported metal.