The invention discloses a coumarin-oxazole-vinyl alpha-glucosaccharase inhibitor as well as a preparation method thereof. The method comprises the following steps: ensuring that a product generated after reaction of salicylaldehyde, ethyl acetoacetate and piperidine is subjected to mixing reaction with N-bromo-succinimide and para-toluenesulfonic acid, and then adding hexamethylenetetramine, so asto obtain white solid after reaction, feeding the obtained white solid into ethanol to dissolve the white solid, feeding concentrated hydrochloric acid, and ensuring that a product generated after reaction reacts with substituted cinnamyl aldehyde, iodine, tert-butyl hydroperoxide and sodium bicarbonate, so as to obtain the coumarin-oxazole-vinyl alpha-glucosaccharase inhibitor which can serve asa main material of an anti-diabetic medicine. The coumarin-oxazole-vinyl alpha-glucosaccharase inhibitor is clear in mechanism of action, stably reduces blood glucose, is safe and non-toxic, high andobvious in inhibitory activity, mature and simple in preparation method, easy to strictly control the quality in industrial production, and mild and non-toxic in preparation conditions, does not produce three wastes, and is environmentally friendly.