The purpose of this study was to evaluate the potential of electron beam to decompose chloramphenicol （CAP） in aqueous solutions. At the absorbed dose of 15 kGy, the decomposition rate of CAP was 95.24%. The degradation of CAP under electron beam irradiation followed pseudo-first-order kinetics. Redox reactions of CAP aqueous solutions with hydroxyl radicals （.OH）, hydrated electrons （eaq） and hydrated atoms （·H） were studied. The increase of the additives would result in the decrease of the degradation efficiency. The concentration of Cl- and NO3- in aqueous solution increased after electron beam irradiation. On the basis of the experimental results, a photocatalytic mechanism was discussed. The rate constant for reactions of .OH and CAP was 9.36×10^7 L/（mol.s） and for reaction of eaq and CAP was 7.33×10^7 L/（mol.s）..OH was supposed to play the key role in the radiation system of aqueous solution. Other free radicals like eaq and .H could also initiate the degradation.
