Abstract: The harm of antibiotics in the environment is of great concern to the ecological environment. The degradation of sulfadiazine (SD) by ozone was studied. The effects of pH, ozone concentration and HC ${\mathrm{O}}_3^{-}$ concentration on the degradation of SD were investigated, and the degradation mechanisms were also analyzed. The results showed that the initial pH, the ozone concentration and HC ${\mathrm{O}}_3^{-}$ all had effects on the SD degradation process, and the initial pH, the ozone concentration and HC ${\mathrm{O}}_3^{-}$ concentration could increase the degradation rate of SD. At initial pH of 9.14, SD concentration of 30 mg/L, ozone concentration of 10.0 mg/L and HC ${\mathrm{O}}_3^{-}$ dosage of 100 mg/L, the SD was primarily removed after a reaction time of 30 min and finally reached a mineralization rate of 39.44% at 120 min. The SD process of ozone degradation was basically in accordance with pseudo-first-order kinetics model. The results of liquid chromatography-mass spectrometry showed that, in the course of ozone oxidation, the formation of p-aminobenzenesulfonic acid (C₆H₇NO₃S) was produced and being further oxidized by ozone and finally mineralized to form CO₂.