The aim of this study is, firstly, to find out what kinds of inorganic species are produced in the photocatalytic oxidation of ammonium-nitrogen containing water and, secondly, to seek the influence of anion for the photocatalytic oxidation of ammonium contained compounds. The photoenergy above 3 eV(λ<415 nm) was effectively absorbed by TiO2 and TiO2/polymer was used to be oxidized NH4-N in wastewater to NO3-N. Existing the anion as Cl-, the rate of photocatalytic oxidation decreased regardless of other condition. This result showed that the chloride ions reduced the rate of oxidation by scavenging oxidizing radical species as OH- and OCl-. Some of the added ion might have blocked the active sites of the catalyst surface, thus deactivated the catalyst.