In this paper， the effects of 0-20 mg/mL pectin on polyphenoloxidase （PPO） enzymatic activity， thermal passivation kinetics， thermal passivation conformational changes and inhibitor action were investigated by ultraviolet spectrophotometer and fluorescence spectrophotometer， respectively. The results showed that PPO activity decreased with the increase of pectin mass concentration. When pectin mass concentration was 20 mg/mL， PPO activity decreased nearly 20%. The thermal passivation kinetics showed that pectin could significantly improve the thermal stability of PPO. Thermal treatment significantly changed the tertiary structure of PPO， while pectin could enhance the conformational stability of PPO under thermal passivation. The inhibitory effect of organic acids on PPO activity was increased by 1.5%-25.7% with the addition of pectin. The results of this study provide theoretical reference for the control of enzymatic browning of fruit and vegetable products.