A TiO2/SiO2 composite prepared by the sol-gel route can produce highly emissive broadband room-temperature phosphorescence at an excitation wavelength of 403 nm. The white phosphorescence of TiO2/SiO2 could be quenched by H2O2. The phosphorescence quenching effect demonstrated excellent sensitivity and high selectivity to H2O2. Furthermore, the phosphorescence of TiO2/SiO2 can be recovered when it is dipped in a hydroxylamine hydrochloride solution. Therefore, the TiO2/SiO2 was used to develop a reproducible phosphorescence sensor for H2O2. It has been successfully applied to the determination of H2O2 in the enzymatic catalytic reaction and real samples.