We report the arsenite adsorption in dark conditions and different pH by CaTiO3 perovskite nanoparticles. Its photocatalytic properties for oxidizing the arsenite As(III), to arsenate As(V), under UV light source have been studied in this research. CaTiO3 (CTO), nanoparticles have a high As(III) removal capacity. Nearly 70% As(III) was oxidized in few minutes, and achieves full oxidizing of As(III) to As(V) in around 90 min. Our results suggest the prepared CTO is a promising candidate for arsenic removal.