The invention relates to the technical field of medicine, food and chemical raw materials, particularly relates to a method for preparing fructose syrup from dextran fermentation broth. The method comprises the following steps: separating out fructose from dextran fermentation broth through plate frame filtration, ceramic membrane microfiltration and 5000-molecular-weight membrane ultrafiltration;performing vacuum concentration at the temperature of 75 DEG C until the concentration is 40%, and performing active carbon decoloration; performing ion-exchange chromatography through cation exchange resin and anion exchange resin; performing vacuum concentration at the temperature of 55 DEG C until the concentration is 71% to obtain the fructose syrup. The preparation method provided by the invention combines the membrane filtration with the traditional fructose syrup production process, the fructose accounting for 52% of saccharose converted products is separated and prepared from the fermentation broth in dextran production, the environmental protection load of enterprises is largely alleviated, therefore the wastes are effectively used, the economic benefits are increased, and the environmental benefits are produced as well. The prepared fructose syrup can be applied to food production and other related industrial productions. The method for preparing the fructose syrup from thedextran fermentation broth adopts process steps of 1, separating the fructose and 2, preparing the fructose syrup.