In order to guarantee the safety of Portuguese oyster (Crassostrea angulata) eaten raw, 13 healthy indexes were examined before and after depuration for 48 h in a non-cyclical flow-through depuration system using ultraviolet light at ratio of oysters to water 1:10, water exchange rate 3 times/h, temperature 28℃, and salinity 28. Then the total bacteria, coliform group and main nutritional components of depurated oysters stored respectively at 4℃ and -18℃ for more than 7 days were detected. The results showed that, after 48h of depuration, the total bacteria and coliform group sharply declined while other indexes changed little; during 4℃ and -18℃ storage, total bacteria and coliform group declined at the beginning and then rose up, but were within safety levels; protein, fat and glycogen decreased slowly whereas lactic acid increased rapidly. In summary, for Portuguese oyster that has been depurated for 48h in UV system, its safety could at least be guaranteed within 6 days of refrigerated or 11 days of frozen storage.