Abstract: A series of composite-crystal nano-TiO2 powder with various contents of rutile were synthesized by the sol-gel method，and were calcined at various temperatures. The effect of rutile content on photocatalytic water-splitting for hydrogen production over composite-crystal nano-TiO2 was studied in the presence of formaldehyde as sacrificial reagent. The results showed that TiO2 with pure anatase showed the best photocatalytic activity，and increase of rutile content caused a decrease of activity，during which a fluctuation was observed. As Pt was deposited on nano-TiO2 surface by the photo-reduction method，the rates of H2 evolution increased first and then decreased with the increase of rutile content. The maximum value，which reached 40.35 mmol/(gcat·h)，was obtained with nano-TiO2 containing 9.7% rutile. A mechanism of the effect of rutile content on photocatalytic water-splitting for hydrogen production over composite-crystal nano-TiO2 was proposed.