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Photoluminescence behavior of TiO2, SiO2/TiO2 binary and Boron-SiO2/TiO2 ternary oxides prepared by the sol-gel method was investigated. The differences in their photocatalytic reactivities of TiO2-based photocatalysts were interpreted in terms of the relationship of the difference in their photoluminescence characteristics. The addition of SiO2 into TiO2 matrix induced new photoluminescence sites, which were due to anchored titanium oxide species (i.e., the formation of Ti–O–Si bonds) located on the surface. The photoluminescence was found to be very sensitive to the presence of oxygen. These new photoluminescence completely disappeared by the addition of boron into SiO2/TiO2 binary oxide, since the emitting sites having a Ti–O–Si bond were destroyed and the new sites having B–O–Ti or Si–O–B bonds were constructed on the surface, being in agreement with the results obtained by FT-IR measurements. For all TiO2-based photocatalysts, a significant quenching of photoluminescence was observed by the addition of oxygen. It was found that the photocatalytic reactivity of TiO2-based photocatalysts for the decomposition of trichloroethylene was clearly associated with their relative quenching efficiencies of photoluminescence; photocatalyst showing high quenching efficiency exhibited a high photocatalytic reactivity.