Abstract: ZnO- TiO₂ composite catalyst was prepared by modified sol-gel method. The microcrystalline structure and light absorption performance of ZnO- TiO₂ were identified by XRD and UV-Vis DRS, respectively. With methyl orange(MO) as the degradation product, the result showed that the photocatalytic activity of ZnO- TiO₂ was affected by the conversion time from sol to gel controlled by changing the content of water and ethanol. when the ratio of n(Zn)∶n(Ti) was 3∶15 and calcination temperature was 500 ℃, the degradation of MO was up to 96.4% under UV irradiation for 5 h. The XRD results confirmed ZnO- TiO₂ appeared mostly anatase TiO₂ and cubic Zn₂TiO₄ phases, and the cubic Zn₂TiO₄ phase was observed only when n(Zn)∶n(Ti)≥3∶15. Compared with the pure TiO₂, the characteristic absorption threshold of ZnO- TiO₂ appeared slight blue shift