The invention provides a blood glucose reduction tablet. The blood glucose reduction tablet comprises, by weight, 5 parts to 85 parts of yellow thorn fruit powder, 10 parts to 25 parts of starch and 5 parts to 30 parts of dextrin. The invention further provides a preparation method and a purpose of the tablet. Through the research, the yellow thorn fruit powder has the good blood glucose reduction function, the amount of insulin can be improved, and the blood glucose reduction effect of the tablet is equivalent to that of glibenclamide of the first-class chemical medicine of the diabetes; however, the difference is that the yellow thorn fruit powder cannot damage the liver, is good in safety and wider in applicable range and is more suitable for serving as food or health care products or medicines for preventing and treating the diabetes.