The photochemical degradation of dimethyl phthalate (DMP) in UV/H(2)O(2) advanced oxidation process was studied and a kinetic model based on the elementary reactions involved was developed in this paper. Relatively slow DMP degradation was observed during UV radiation, while DMP was not oxidized by H(2)O(2) alone. In contrast, the combined UV/H(2)O(2) process could effectively degraded DMP, which is attributed to the strong oxidation strength of hydroxyl radical produced. Results show that DMP degradation rate was affected by H(2)O(2) concentration, intensity of UV radiation, initial DMP concentration, and solution pH. A kinetic model without the pseudo-steady state assumption was established according to the generally accepted elementary reactions in UV/H(2)O(2) advanced oxidation process. The rate constant for the reaction between DMP and hydroxyl radical was found to be 4.0 x 10(9) M(-1)s(-1) through fitting the experimental data to this model. The kinetic model could adequately describe the influence of key factors on DMP degradation rate in UV/H(2)O(2) advanced oxidation process, and could serve as a guide in designing treatment systems for DMP removal.