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In our previous study, the effect of temperature for fabrication ZnO-SiO2 nanocomposite had been investigated. It was found that the optimum condition for the photocatalytic activity was obtained when the nanocomposite was synthesized at temperature of 400 °C. In the present study, the effect of SiO2 loading on the ZnO-SiO2 nanocomposite were investigated as well as the photocatalytic performance. ZnO-SiO2 nanocomposites have been synthesized by a combination liquid and gas-phase processes. Colloidal silica was prepared by sol-gel method, where water glass was used as a precursor. The water glass was diluted into demineralized water and passed it into activated cation resin using HCl 2 M to allow the exchange of H+ and Na+ ions. While, ZnO was obtained by decomposition of Zn(CH3COO)2.2H2O inside tubular spray reactor. The effect of SiO2 concentration ranging from 0 to 2 %wt was used. Characterization of ZnO-SiO2 nanocomposites was carried out by morphological analysis with scanning electron microscope (SEM), crystallinity analysis with X-ray diffraction (XRD), functional group analysis with Fourier transform infrared (FTIR) and photocatalytic test by evaluating the degradation rate of methylene blue (MB) under UV and sunlight irradiation. It was found that the best photocatalytic performance was attained when the concentration of SiO2 was equal to 1 % wt at temperature of 400°C. The degradation efficiency reached 95 % using this parameter. [ABSTRACT FROM AUTHOR]