Ru–B/ZrO2 catalysts using monoclinic, amorphous, and tetragonal ZrO2 as supports were prepared and used for liquid-phase hydrogenation of benzene to cyclohexene. It is identified that both the Lewis acid sites and the Brønsted acid sites existed on monoclinic ZrO2 (ZrO2-M), while there were only Lewis acid sites on amorphous (ZrO2-A) and tetragonal ZrO2 (ZrO2-T). The amount of acid sites on ZrO2-T was the lowest. In liquid-phase hydrogenation of benzene to cyclohexene, the Ru–B/ZrO2-T catalyst exhibited the highest selectivity and yield of cyclohexene, with the maximum yield of cyclohexene being 47%. These results suggest that for ZrO2-supported Ru–B catalysts, the lower was the amount of acid sites on ZrO2, the higher was the selectivity to cyclohexene. Also, the presence of the Brønsted acid sites on ZrO2 is probably adverse to the selectivity toward cyclohexene.