The invention relates to an 
ophiopogon japonicus extract, a preparation method and the hypoglycemic application thereof. The preparation method of the 
ophiopogon japonicus extract comprises: 
ophiopogon medicine is taken to be decocted for 1-3 times, added with water by 5-20 times every time, then decocted for 30-120min every time, and filtered and merged into water-decocted liquid; after being concentrated to the density of 1.05-1.35g / ml, the obtained water-decocted liquid is added with 
ethanol until the 
alcohol content has the 
volume percent of 50-80%, and is collected and precipitated after staying over night; the 
precipitation is separated and purified by 
sephadex column, and then processed by vacuum 
freeze drying, so that white loose flocculent 
crystal which is the 
ophiopogon japonicus extract can be obtained, and the extract has the 
sugar content of 90-98%( based on 
fructose) as well as the molecular weight within the range of 500-2000. Animal experiments prove that the 
ophiopogon japonicus extract has remarkable hyperglycemic effect, and the action mechanism of the 
ophiopogon japonicus extract can be further explained by vitro experiments; the result shows the ophiopogon japonicus extract can reduce 
blood sugar levels by inhibiting the activity of alpha-glucosaccharase in alimentary canal, reduce the absorption for glucose by intestinal villi and the protective action for 
islet cells. Therefore, the extract can be used for developing 
medicine for treating 
type II diabetes.