Cost-effective MoS2 cocatalyst usually displays a low alkaline photocatalytic H2-evolution rate due to its sluggish hydroxyl-desorption kinetics and inert in-plane S atoms. Herein, a new strategy of swapping catalytic sites was developed to accelerate hydroxyl desorption of MoS2 cocatalysts, and the in-plane S-Hads bonds were effectively reinforced, realizing a rapid alkaline H2-evolution dynamic. Via a complex-mediated photodeposition pathway, S-rich RuMoS2+x nanodots incorporated with ultralow Ru atoms are perfectly anchored onto TiO2 nanoparticles to synthesize S-rich RuMoS2+x/TiO2 photocatalysts. In an alkaline enviroment, the S-rich RuMoS2+x/TiO2-7 photocatalyst delivers the highest H2-evolution rate, which is superior to the S-rich MoS2+x/TiO2 and crystalline MoS2/TiO2 sample. It is found that the catalytic sites for hydroxyl adsorption/desorption have been reversed from Mo to Ru atoms, and the Ru incorporation decreases the electron density of in-plane S atoms, thus accelerating hydroxyl desorption and reinforcing interfacial S-Hads to enhance alkaline H2-production rate of the S-rich RuMoS2+x/TiO2 photocatalysts.