Wastewater produced from industrial processes contained large quantities of organic, inorganic matters and toxic materials, which are difficult to degrade with traditionally biological method. Photocatalysis reaction can oxidize a wide variety of organic compounds to harmless inorganics such as CO2, H2O and mineral acids. This study is the effect of flow pattern in semi-batch mode photocatalytic system, which includes two reactors coated with TiO2. In our present work, it was found that the linear velocity and swirl flow in thin film reactor affect the increasing of removal efficiency of non-degradable organic compounds.