The quality of used frying oil degraded due to the presence of products degradation, such as; PV and FFA which formed during the frying process. PV and FFA are harmful to human health. The photocatalytic activity of TiO2 thin film has been applied in various fields, especially in the environment. The aim of this study is to evaluate photocatalytic activity of TiO2 thin film for reducing PV and FFA in used frying oil. The TiO2 thin films were deposited on glass substrate by spray coating method at a temperature of 450 °C. The TiO2 precursor solution was prepared by mixing TTiP, AcAc, and ethanol. The thin films were varied into two conditions; as-deposited and annealed at a temperature of 500 °C. The morphology, crystalline structure, and optical properties of the thin films were characterized by scanning electron microscope (SEM), X-ray Diffraction (XRD), and UV-VIS spectrophotometer, respectively. Photocatalytic process was carried out by putting TiO2 thin film in used frying oil and irradiated by sunlight. The result showed that both of TiO2 thin films were still amorphous in nature. However, there was a peak with low intensity for annealed TiO2 thin film which corresponding to the TiO2 anatase crystals plane of (101). Annealing process improved crystallinity and changed the shape morphology of TiO2 thin films. The band gap was found to be 3.59 eV for as-deposited TiO2 thin film and 3.49 eV for the annealed-TiO2 thin film. Photocatalytic process shows that TiO2 thin films reduced FFA and PV of used frying oil up to 67.10% and 79.15%, respectively. The photocatalytic activity of annealed TiO2 thin film was higher than as-deposited TiO2 thin film. The results indicated that TiO2 thin film photocatalyst potential as the new alternative method to purify used frying oil.