Sweetening composition and preparation method and use thereof

A method for preparing a sweetening composition from the leaves of Rubus suavissimus S. Lee, comprising:

• S1. pretreatment:
• crushing raw materials, removing a solid of a leaf tissue including glycoside from a solid of the raw materials by a cyclonic separation, separating mesophyll fragments from the raw materials, and collecting the mesophyll fragments;
• S2. extraction:
• extracting the mesophyll fragments with water as a solvent to obtain an extract solution;
• S3. removal of phenolic hydroxyl-containing components:
• allowing the extract solution to pass through a polar macroporous adsorption resin such that the phenolic hydroxyl-containing components are adsorbed, and collecting an effluent;
• S4. concentration and purification with a nanofiltration membrane:
• allowing the effluent collected in said S3 to pass through a nanofiltration membrane with a pore diameter of 1 to 2 nm for concentrating and purifying, and retaining a retentate solution;
• and
• S5. water-phase crystallization:
• freezing the retentate solution obtained in said S4 into a solid, then thawing, and crystallizing at a temperature of 0° C. to 10° C. to obtain crystals of a sweetening composition.