Melanosis is one of the problems for Penaeus vannamei Boone because of the high activity of polyphenol oxidase (PPO).The effect of boiling(BT) and steaming(ST) on inhibiting PPO and maintaining the quality of shrimps was studied.Comparing with ST,there was greater inhibition of PPO,less moisture content,better effect of sterilization,yet greater loss of amino nitrogen after BT for an equal time.