Most of water sources throughout the world contain natural organic matter (NOM), which is the best description as a complex mixture of organic compounds. The effect of iron ion on removal efficiency of dissolved organic carbon (DOC) using UV/TiO2 photo catalytic oxidation (TiO2) was examined. In this quasi-experimental study, the different variables such as pH value, contact time, various concentrations of TiO2, FeCl2 on the removal efficiency of DOC by the UV/TiO2 on raw water of Zayandehroud in Isfahan were studied. The results were analyzed by using Pearson correlation coefficient test and SPSS software. Removal efficiency DOC improved as the amount of catalyst was increased. Maximum removal efficiency was achieved during acidic conditions (pH=3) within 60 minutes of contact time. The removal efficiency of DOC by the UV/TiO2 decreased with increase of contact time. The presence of iron ions increased the rate of DOC removal by the UV/TiO2. Removal efficiency of dissolved organic carbon increased when ionic strength and initial concentration of Ferric Chloride was increased. Also, by adding particles of Ferric Chloride, Removal of dissolved organic carbon increased to 98% in comparison with absence of iron ion (78%).