The invention discloses a method for preparing cubilose extract used in 
cosmetics. Steps are as follows: (1) 
cryogenic grinding cubilose, sieving, adding water 20 times the weight of the dry cubilose, ultrasonic extracting at 
room temperature for 1h, filtering, (2) adding water 30 times the weight of the dry cubilose into the 
filter cake, boiling for 60 minutes under mechanical stirring, (3) cooling to 
room temperature, regualting pH to 9.8 with Na2CO3 solution, adding alkali 
protease 1.5% the weight of the dry cubilose, carrying out 
hydrolysis in water bath at 55deg.C under mechanical stirring, (4) deactivating 
enzyme at 85deg.C for 20min, (5) cooling to 
room temperature, regulating pH to neutrality with thin HCl, (6) filtering, combining the filtrate with ultrasonic extract, and 
freeze drying to obtain powdered cubilose extract. The invention has simple process, good extract water-
solubility, high extraction yield, rational product molecular 
weight distribution, good wetness protection, high product whitening activity, and good product stability; and avoid the influence of boiling to the thermo instable 
active ingredient in 
hydrolysis technology. The obtained cubilose extract is suitable for using as cosmetic compounding.