Surface passivation is one of the key factors to the high efficiency solar cells.In this paper (Al2O3)x(TiO2)1-x dielectric films used as backside surface passivation for crystalline silicon solar cells were prepared by the low-cost sol-gel method.The relation between the passivation properties of the films and the preparation technology was investigated using orthogonal experiment method.The technology of the preparation was optimized.The surface passivation characteristic of the (Al2O3)x(TiO2)1-x thin films is in correlation with sintering temperature.The surface recombination velocity of 1260cm/s of the thin layers can be achieved at sintering temperature 400℃.The (Al2O3)x(TiO2)1-x dielectric films also have feasible optical properties which can be acted as backside reflector if combined with metal contact.