The invention discloses a hawthorn leaf injection for treating cardiovascular diseases, which is prepared from hawthorn leaf extract and a solvent for injection, and the solution contains total flavonoids in an effective therapeutic amount. The hawthorn leaf extract is prepared by the following method: a. take hawthorn leaves, add 40-60% ethanol to extract, filter, recover ethanol, concentrate to a relative density of 1.12-1.14, dilute with water, and refrigerate for 12-24 hours. Aspirate the supernatant, filter the lower layer, combine the filtrate and the supernatant, and elute until the reaction of concentrated sulfuric acid of α-naphthol is negative; b. Collect the ethanol eluate until the reaction of magnesium hydrochloride powder is negative, recover the ethanol, concentrate, Extract with ethyl acetate, recover ethyl acetate from the extract and concentrate to dryness to obtain extract I; extract the water layer with n-butanol and concentrate to dry to obtain extract II; the present invention has effects on the ejection ability and oxygen metabolism of the heart It has obvious improvement effect, can significantly increase cardiac output and stroke volume, reduce arterial blood oxygen content, increase venous blood oxygen content, reduce myocardial oxygen consumption and myocardial oxygen utilization rate, and improve myocardial blood and oxygen supply.