In this work, SiO2/TiO2 nanocomposites have been successfully synthesized hydrothermal with rapid reaction time under supporting of microwave at power of 150 W, for 1 h using SiO2 from rice husk ash (RHA) as silica source in Vietnam. The SiO2/TiO2 nanocomposites were characterized by UV–vis spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), fourier transforminfrared spectroscopy (FTIR), and X-ray diffraction (XRD). It was also demonstrated that the SiO2/TiO2 nanocomposites were extremely good catalytic activity and high stability. Our results show that SiO2/TiO2 nanocomposites were obtained with particle sizes in range from 10-30 nm and highly pure formed in 1 h. Moreover, the SiO2/TiO2 nanocomposites’ stability increased to more than 24 h for investigating their catalytic activity in the saltwater medium with highly treatment efficiency respective about 66.4% and 75.2% under the lighting conditions of the sunlight and the UV-light in 3 h for comparisons.