The degradation efficiency and first-order reaction kinetics of 2,4-DCP with UV/PS process at 25 ℃,under different temperature and different pH conditions were investigated; meanwhile, the intermediate products and the possible reaction pathways of 2, 4-DCP degradation by UV/PS were speculated. The types and yields of disinfection by-products generated by oxidizing 2,4-DCP with PS,UV and UV/PS during chlor(am)tion processes. The results showed that the removal rate of 2, 4-DCP can reach as high as 86.4 % with UV/PS process, which indicated 2, 4-DCP can be highly degradated by UV/PS, and the reaction fitted the pseudo-first-order reaction equation. The degradation rate increased with the increase of temperature, fitted the first-order reaction kinetics and Arrhenius formula fitting model, the linear were better. PH value increased from 5 to 9, and the reaction rate constant first increased and then decreased, which was the highest at pH=7.0. The actual water including of Xi-cheng reservoir, You-che reservoir, Xi-dong water works and tap water were prepared as the background of 2, 4-DCP solution ,the photo catalytic oxidation degradation efficiency of 2,4-DCP solution were 73.5%, 80.2%, 82.4% and 87.4%, respectively. three kinds of carbonaceous disinfection by-products containing chloroform(CF) , two chloroacetic acid (DCAA)and acetic acid(TCAA), two kinds of nitrogen disinfection by-products containing dichloroacetonitrile (DCAN) and trichloronitromethane (TCNM) were determined with GC-MS during degradation 2,4-DCP by PS,UV and UV/PS processes with chlor(am)ination process, the UV and UV/PS process can significantly reduce the total yields of DBPs caused by 2,4-DCP as the precursor.