FIELD: chemistry.SUBSTANCE: present invention relates to a method for preparing a composition in form of particles, containing anhydrous crystalline 2-glucoside ascorbic acid, and can be used in pharmaceutical industry. Proposed method comprises allowing cyclomaltodextrin glucanotransferase to act on a solution, comprising either liquefied starch or dextrin and L-ascorbic acid as materials, and then allowing a glucoamylase to act on resulting solution to obtain a solution, containing 2-O-α-D-glucosyl-L-ascorbic acid, with 2-O-α-D-glucosyl-L-ascorbic acid production yield of at least 27 wt%； purification of obtained solution, containing 2-O-α-D-glucosyl-L-ascorbic acid, to obtain content of 2-O-α-D-glucosyl-L-ascorbic acid of more than 86 wt%, in terms of dry weight of solid substance； precipitation of anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid from purified solution with content of 2-O-α-D-glucosyl-L-ascorbic acid of more than 86 wt%, in terms of dry weight of solid substance, by method of controlled cooling or by pseudo-controlled cooling； collection of precipitated anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid and ageing, drying and optionally milling collected anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid without dissolution and recrystallisation to produce a composition in form of particles, containing anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid, which contains 2-O-α-D-glucosyl-L-ascorbic acid in an amount in terms of dry weight of solid substance, of more than 98.0 wt%, but less than 99.9 wt% has crystallinity of anhydrous crystalline 2-O-α-D-glucosyl-L-ascorbic acid at least 90%, when calculating based on x-ray powder diffraction profile of composition in form of particles； where method of controlled cooling is a method of cooling, where temperature T of solution at a time t is expressed by formula T=T0-(T0-Tf)(t/τ)3, where τ is operating time, set for crystallisation stage, T0 is temperature of solution at beginning of
