An excited-state Rose Bengal (RB) nonradiative process caused by proton-induced quenching makes the capacity of photoelectrons to reduce water weak, which crucially influences the efficiency of hydrogen generation for RB-sensitized photocatalytic systems. In this work, we introduced a low content of dimethyl sulfoxide (DMSO) to form a water–DMSO mixture solvent, which significantly inhibited the nonradiative process. The lifetime of the excited electrons was increased remarkably. The hydrogen generation activity in a water–DMSO mixture solvent was 4.48 times higher than that in the single water solvent. The highest apparent quantum efficiency (AQE) of 44.3% was reached at 550 nm. A small amount of DMSO could break the partial network through hydrogen bonding, increase the RB hydrophobicity, and suppress the excited-state RB nonradiative process.