In order to investigate the degradation law and characteristics of β-lactam antibiotics during ozone oxidation, four typical β-lactam antibiotics in water were treated by direct ozone oxidation. The degradation effect of ozone on typical β-lactam antibiotics under different pH values was studied. Quenching experiments were adopted to explore the degradation mechanism,analyze intermediates and speculate the degradation path. Results showed that the degradation of amoxicillin and cephalexin was not significantly affected by changing pH, penicillin sodium was inhibited in acidic condition, and ceftriaxone sodium was promoted in alkaline condition.The results of quenching experiments showed that TBA can promote the degradation of amoxicillin and cephalexin, indicating that the degradation of amoxicillin and cephalexin was dominated by direct oxidation of O₃.With the increase of TBA concentration, the inhibition effect to penicillin and ceftriaxone sodium was more and more significant, which indicated that penicillin and ceftriaxone sodium were indirectly oxidized by ·OH.Amoxicillin, cephalexin, penicillin sodium and ceftriaxone sodium produced 4, 6, 3 and 3 main intermediates during ozonation, respectively. The degradation pathways were composed of β-lactam ring breaking, demethylation, hydration and addition etc.