Abstract:This paper studied the relationship of Porphyra yezoensis between water activity and water content. Then optimizated the microwave sterilization technology. The results showed that the moisture content of seaweed and microwave treatment time on the effect of microwave disinfection significantly affected. In the water activity of 0.75 （water content 18.8 %，wt %），sterilization time 20 s and the power 600 W，The best effect of microwave sterilization was obtained. And compared to conventional thermal sterilization（85 ℃/30 min、100 ℃/15 min），microwave sterilization have advantages of shorter sterilization time，better bactericidal effect and less damage of nutritional material.