To investigate the environmental degradation process of phthalic acid esters (PAEs).The PAEs were detected by HPLC. We used the system of ultraviolet light, TiO2 and hydrogen peroxide to promote the photodegradation of PAEs in water.The photodegradation of PAEs was consistent with the first level kinetics. The maximal photodegradation of PAEs occurred at the 2.0 g/L of TiO2, pH 6.0, and 2.0% of H2O2. The importance of these environmental factors in promoting the photodegradation of PAEs were in the following orders: initial concentration of PAEs, radiation time, pH value, concentration of H2O2, and concentration of TiO2.The system of ultraviolet light, TiO2 and hydrogen peroxide was effective in promoting the photodegradation of PAEs.