This paper aims to examine the separation of ultrafine titanium dioxide (TiO2) ptotocatalyst from its aqueous suspensions and its reuse by cross-flow ultrafiltration (CFU) process. Initially, the effects of various parameters, such as feed concentration, transmembrane pressure, cross-flow velocity, pH, electrolyte and membrane molecular weight cut-off (MWCO) on the flux were investigated. Thereafter, the activity of reused photocatalyst for dye wastewater by CFU and coagulation processes was compared respectively. The results of this investigation reveal that: (1) a complete separation of TiO2 from its aqueous suspensions can be obtained by an ultratfiltration process compared to coagulation process; (2) it is more efficient to maintain high activity of the separated TiO2 by CFU process than that of coagulation process. Therefore, the combined slurry photoreactor and CFU process in this study can be an attractive option for controlling pollutants in water.