Photolysis and debromination of bromophenols were widely investigated previously. However, the role of reactive species especially hydrated electrons (eaq−) in their degradation was overlooked. Therefore, in the study, generation and role of the reactive species generated during the photolysis of bromophenols were identified and evaluated by using 2,4,6-tribromophenol (TBP) as a model at different pH values from 4 to 11 under anaerobic condition. It was found that photolysis of TBP solution under UV irradiation (254 nm) yielded organic radicals (C•), hydrogen radicals (H•) and eaq−. By using nitrite and monochloroacetic acid (MCAA) as scavengers of H•/eaq−, the role of UV direct photolysis, H• and eaq− in degradation of TBP was quantitatively assessed at different initial pH (pH0) values. UV irradiation induced direct photolysis of TBP was mainly dependent on its molar absorbance coefficient (ε) at 254 nm. Contribution rate of UV irradiation to degradation of TBP was about 60% at pH0 4, 7 and 11. Interestingly, the contribution rate of eaq− was high as 35.8%-40% at pH0 4–11, while the contribution rate of H• was negligible (<2.5%) at these pH values. Accordingly, UV and eaq− induced degradation and debromination pathways of TBP under UV irradiation were proposed. This work gains deep insight into the photolysis process of bromophenols, and clarifies the important role of eaq− in photo-degradation of bromophenols.