Preparation method of psicose crystals

The present invention relates to a preparation method of psicose crystals. The preparation method comprises the following steps: carrying out chromatographic separation of psicose liquid after an enzymatic conversion is finished and purifying the psicose to a purity of 98.5% or more; concentrating the purified psicose to a solid content by mass of 75-85% and conducting rapid cooling to 35-45 DEG C; adding seed crystals, keeping temperature at 35-45 DEG C and a vacuum degree of -0.03 to -0.09 MPa, and performing constant-temperature evaporative crystallization; and performing centrifugal separation to obtain crystals with a particle size larger than 60 meshes, and conducting washing and drying to obtain the psicose crystals. The technical means of controllable evaporation, constant-temperature crystallization, etc. are used to solve a problem that fine crystals are generated under a condition of high supersaturation degree, greatly improve particle diameter of the crystals, enable one-time crystallization yiel