Sr^2＋-doped nano TiO₂ colorless and transparent hydrosol with an average particle size of 6 nm was synthesized by a novel complexation-controlled hydrolysis method at room temperature by using TiCl₄, organic carboxylic acid, NH₃•H₂O, Sr(OH)₂•8H₂O, and D-sorbitol etc as raw materials. Subsequently, the nanoscaled thin films were prepared by ordinary spraying technology. The phase structure, composition, particle size, absorbance spectrum, and contact angle of samples were characterized by XRD, nano laser particle size analyzer, AFM, EDS, ultraviolet-visible spectrophotometer, and optical contact angle tester, respectively. In addition, the influence of reaction conditions in the synthesis process was also studied. The nanoscaled thin films prepared by Sr^2＋-doped nano TiO₂ hydrosol exhibit optimal photocatalytic performance when the doping content of Sr^2＋and refluxing time are 1.8% and 60 min, respectively. The degradation efficiency of acid red 3R dye solution with concentration 50 mg/L has reached 99% after exposed to sunlight for 60 min. Furthermore, the contact angle of the thin film sample is 0.91 degree, indicating the superhydrophilic property of the sample.