In the current work, a peroxo titanium complex (PTC) solution was used as a novel water-soluble precursor to fabricate H2Ti2O5·H2O and the SiO2/H2Ti2O5·H2O-nanochain composite at low temperature (90-100 °C). The average width of H2Ti2O5·H2O nanochains is 4.5 ± 1.5 nm. Under full-spectrum irradiation, the Si/Ti-nanochain composite showed good UV-visible light absorption and excellent photocatalytic activity, which is 2.8 times that of P25. In the composite, SiO2 not only contributes to the formation of nanochains and improves the catalytic performance of H2Ti2O5·H2O but also reduces the refractive index of the complex. When coated on transparent organic substrates, the composite thin film exhibited excellent antireflective (as high as 99.3% on PC and 98.9% on PMMA) and self-cleaning properties. Pencil hardness, washing, and tape adhesion tests showed favorable adhesion-to-substrate and mechanical robustness of thin films, which make them extremely attractive for applications as highly transparent and self-cleaning thin films on lenses, photovoltaic cells, and windows of high-rise buildings.