Abstract: As a new pollutant,propranolol pose a great threat to the environment and human health.The effectively removal of propranolol in the environment is becoming the focus of attention.In this dissertation,propranolol photocatalytic degradation under the UV/Fenton conditions was investigated by using density functional theory at B3LYP/6-31+G(d). This study found photocatalytic of propranolol started by OH radical addition, addition on the different carbon positionsof its naphthalene ring, and then further broken the C-O bond or hydrogen abstraction,finally the formation of stable naphthol, O-naphthol, 1,4-dinaphthol and 1,6-dinaphthol.Consistent with the experiment, the process and confirm from the angle of theory ,and the reaction path which havent been tested in experiment is feasible in theory.