In the field of quantum dots (QDs)-sensitized solar cells, semiconductor QDs sensitizer with a moderate band gap is required in order to sufficiently match the solar spectrum and achieve efficient charge separation. At present, changing the size of QDs is the main method used for adjusting their band gap through quantum size effect, however, the pore sizes of mesoporous TiO2 film set a limit on the allowed size of QDs. Therefore, the tuning of electronic and optical properties by changing the particle size could be limited under some circumstances. In this paper, high-quality aqueous CdS(x)Se(1-x) QDs sensitizer is successfully synthesized and effectively deposited on a mesoporous TiO2 film by a one-step hydrothermal method. In addition to size, alloy QDs provide composition as an additional dimension for tailoring their electronic properties. The alloy composition and band gap can be precisely controlled by tuning the precursor (Se/Na2S·9H2O) ratio while maintaining the similar particle size. By using such CdS(x)Se(1-x) sensitized TiO2 films as photoanodes for solar cell, a maximum power conversion efficiency of 2.23% is achieved under one sun illumination (AM 1.5 G, 100 mW cm(-2)).