Kinetics on degradation efficiency of medroxyprogesterone (MPA) by ozonation was investigated in this paper. And the operating parameters such as MPA initial concentration, ozone dosage, pH and radicals scavenger (HCO3-) were further discussed. Results showed that MPA could be degraded effectively by ozonation, with a first-order kinetics in continuous ozone aeration system and a second-order kinetics in semibatch ozone aeration system, when the initial concentrations of MPA were 3, 5, 10 mg x L(-1). The increases of pH and the addition of HCO3- would bring negative effects to the degradation of MPA. The degradation efficiency of MPA decreased from 89.8% to 54.8% with pH increase from 3.10 to 9.02, and the rate constant k decreased from 0.1463 L x (mg x min)(-1) to 0.049 5 L x (mg x min)(-1) and the degradation efficiency decreased 22.2 percentage points with the addition of HCO3-, in semibatch aeration system.