The porous structure and honeycombed structure of granulated blast furnace slag formed by alkali activation (AGBFS) can be used as a promising photocatalysts substrate for the photocatalytic removal of atmospheric or water pollutants. In this study, photocatalytic activated slag granules were synthesized by loading TiO2 on AGBFS with immersion method. The physicochemical properties and NOx removal performance of activated slag granules/TiO2 photocatalysts were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and photocatalytic performance test. The effects of slag particle sizes and nano-TiO2 loading concentrations on photocatalytic efficiencies of NOx removal were also investigated. It was found that the De-NOx performance of activated slag granules/TiO2 photocatalyst increased with the increasing of slag particle size in low TiO2 loading concentration situation, while increasing the TiO2 loading concentration would result in the opposite De-NOx performance as slag size increased. Nevertheless, for the same size activated slag, the photocatalytic efficiency of activated slag granules/TiO2 photocatalyst gradually improved with the increase of loading concentration of TiO2.