We demonstrated photocatalytic hydrogenation coupling of acetone into 2,3-dimethyl-2,3-butanediol with formic acid as a hydrogen source. In this synergetic system, the conversion of acetone and formic acid was dramatically increased than that in the individual reaction system. Consequently, the selectivity of 2,3-dimethyl-2,3-butanediol was relatively high over that of NaTaO3 and Na2Ti3O7 photocatalysts. Additionally, in this acetone-formic acid reaction system, the presence of acetone can effectively restrain the generation of CO during the decomposition of formic acid.