The invention belongs to the technical field of medicinal product research and development. The invention relates to a preparation method and use of Syringa pubescens bark extract. The method comprises: leaching 40-mesh Syringa pubescens bark powder with 70-percent ethanol in an amount which is 6 to 8 times that of the Syringa pubescens bark powder at room temperature for 8 to 10 hours, standing and filtering; leaching the filter residue with 70-percent ethanol in an amount which is 8 times that of the filter residue, leaching the filter residue with 70-percent ethanol in an amount which is 6 times that of the filter residue, performing ultrasonic treatment for 30 minutes, combining filtrate, recovering solvent and obtaining total extract; extracting the total extract with petroleum ether, ethyl acetate, water saturated n-butyl alcohol respectively at three times; and combining the petroleum ether layer extract solution, the ethyl acetate extract solution and the n-butyl alcohol extract solution, concentrating under vacuum, performing freeze drying, and obtaining the petroleum ether layer extract, ethyl acetate extract and n-butyl alcohol extract of the Syringa pubescens bark. The product of the invention has a remarkable removing effect on hydroxyl radicals, can be developed into a natural antioxidant medicament to be used as a substitute for synthetic antioxidant in treating diseases caused by an overlarge amount of radicals in the body.