Research of 2,4‐chlorophenol and 2,4,6‐trichlorophenol in aqueous solution using the photo‐Fenton process was conducted in two parts. The first part of the study explored the treatment efficiency and reaction rate expression of 2,4‐chlorophenol and 2,4,6‐trichlorophenol. With respect to the simulated experimental data, the relationship between the reaction rate for 2,4‐chlorophenol and 2,4,6‐trichlorophenol and H2O2concentration was expressed as a first‐order reaction and that between the reaction rate and the Fe(II) concentration was a saturation‐type reaction. In the second half of this study, chlorohydroquinone, catechol, dichlorocatechol, and dichlororesorcinol were found in the photo‐Fenton process by GC/MS. Some of these identified intermediates were more toxic than the primary compound.