This work centered on the effects of F modification on the interfacial behaviors between Pt clusters and TiO2, especially oxygen vacancy (Ov) enriched TiO2 (V-TiO2), under UV pretreatment for improving the photocatalytic activity. F modification benefited the reduction from PtOx to Pt-0 and Pt-O-ads under UV pretreatment for F modified TiO2/Pt (F-TiO2/Pt), resulting in the increasing of photocatalytic reactive sites. While for F modified V-TiO2/Pt (F-V-TiO2/Pt) case, F preserved the excellent property of Ovs on optically modulating Pt clusters to smaller size, which further enhanced the photocatalytic reactivity of the UV pretreated F-V-TiO2/Pt. F chemically stabilized Ovs on F-V-TiO2/Pt during the UV pretreatment, leading to a more stable photocatalytic activity than F-free ones. The significantly enhanced performances of F modified catalysts with various UV pretreatment times were evaluated with CO photocatalytic oxidation. The best CO photocatalytic constant rates of F-TiO2/Pt and F-V-TiO2/Pt obtained at 4.0 h of UV pretreatment time were ca. 6.6 times and ca. 4.2 times as high as that untreated ones, respectively.