The invention provides an application of rosa roxburghii tratt fruit polysaccharides in preparation for blood glucose-reducing medicines, heath products or foods. Researches on the application provided by the invention find that the rosa roxburghii tratt fruit polysaccharides have a good blood glucose-reducing function, can increase an insulin amount, and have a regulation effect on the activities of the corresponding ROS metabolism-related enzymes, that is, the activities of superoxide dismutase, catalase, and glutathion peroxidase to a certain extent. Meanwhile, the application provided by the invention further finds that the effect of a rosa roxburghii tratt fruit high-dose group is equal to the effect of glibenclamide, although glibenclamide is a first-line medicine for treating diabetes, glibenclamide finally causes the hypoglycaemia and kidney diseases of patients, and even causes death in case of being greatly taken for a long time; conversely, rosa roxburghii tratt fruits are edible berries, good in safety, and more suitable for being used as foods, health products or medicines for treating and preventing diabetes.