Changes of polyphenol oxidase (PPO),pectin methylesterase (PME) and related qualities in cloudy apple juice from apple slices treated by high pressure carbon dioxide (HPCD) were investigated in this study which is divided into three sections.Temperature study:from 25 to 65 ℃ at interval of 10 ℃,at 20 MPa for 20 min; Time study:from 10 to 50 min at interval of 10 min,at 25℃ and 10 MPa; and Pressure study:from 10 to 30 MPa at interval of 10 MPa,at 25℃ for 10 min.PPOs were completely inactivated by HPCD in these three studies apart from 10 min in time study,residual activity (RA) of which was 18.98%.RA of PME with HPCD was 18% at 65℃ in temperature study,46.0% for 50 rain in time study,and 41.2% at 30 MPa in pressure study.RA of PME displayed decreasing tendency as treatment temperature increased,pressure enhanced and time prolonged.