Abstract: The effect of high pressure carbon dioxide (HPCD) on polyphenoloxidase (PPO) activity, light transmission rate, color, browning degree of fresh pear juice were investigated, its storage stability was also analyzed.The result showed that the residual PPO activity was 19% as exposed to HPCD (30MPa- 40℃ for 60min) , which was much lower than that as exposed to thermal treatment at 40℃ for 60min, indicating that there was positive synergistic effect of temperature and pressure come from CO 2 during inactivation of enzyme by HPCD.The PPO activity was stabile during storage at 4℃ for 8 weeks.HPCD inhibited reduction of light transmission rate and browning, maintained excellent color, and obtained excellent quality during storage at 4℃ for 8 weeks.The PPO was also inactivated by thermal treatment at 90℃ for 10min effectively.Though nonenzymic browning was facilitated, light transmission rate was decreased, turbidity was accelerated by high temperature treatment, it was unfavourable for maintaining good quality of pear juice.