Abstract: Simple and quick method was used to prepare nano-silver colloids, and common food preservation was studied in this paper.Silver nitrate and sodium citrate as reactants with microwave-assisted synthesis method wad used to prepare the nano- silver colloids. Choose the nano- silver as fresh- keeping reagents under the reaction time of 8, 15 and 20min, and strawberry as fresh- keeping targets, so as to study the fresh- keeping properties of nano-silver colloids.According to the testing of each freshness target of strawberry in period of storage, the result showed that three kinds of nano- silver colloid had fresh- keeping activity. The nano- silver colloids with reaction time of 15min had the best fresh-keeping effect, and in the test items, the RSD of the weight loss rate, good fruit rate, titrable acidity and reducing sugar content were within 1.5%.The results provided some theoretical basis for nano-silver colloids applying to food preservation and antibacterial.