Abstract: Polyphenol oxidase (PPO) of broccoli was investigated through spectrophotometric method by using catechol as substrate.And an examination method for the activity of broccoli PPO was established.Results showed that the optimum conditions for detection of PPO activity from broccoli were as followings:absorption wave length 415nm, 35℃ and pH7.2. The processing technology about blanching was investigated, results indicated that optimum condition of blanching was at 95℃ for 90s, after blanching treated with cooling type of ice water immediately. Under the condition, the PPO activity of broccoli could be effectively passivation and the loss of color could reduce effectively, giving a good color retention.