Ofloxacin(OFX) has increasingly become a serious environmental problem. Because of high-efficiency, highspeed and no secondary pollution, the γ-irradiation is used in the degradation of antibiotic in water environment. Nanostructure-CeO2, which is inexpensive and has excellent catalytic performance, can be used to promote the γ-irradiation degradation of pollutants. The degradation products of OFX and the catalytic mechanism of CeO2 are analyzed. The result shows that the degradation rate can reach 99% in 2 kGy γ-irradiation dose after adding CeO2, obviously better than that without catalyst. And by contrast, it is found that the catalyst performance of CeO2 is better than that of H2O2. Finally, the degradation products and the hydroxyl attack reaction pathway of OFX are researched by the liquid chromatography-mass spectrometer (LC-MS) method.