The invention belongs to the technical field of chemical engineering and particularly relates to an extract prepared by using willow barks or willow branches as raw materials, and a method for preparing high-purity salicin, aiming at providing a method for extracting high-content salicin from the willow barks or the willow branches. The method comprises the following steps of: (A) taking the willow barks or the willow branches as the raw materials and carrying out extraction by using an aqueous or alcoholic solution, (B) filtering an extracted solution, (C) carrying out resin adsorption separation on a filtrate, (D) decolorizing, and (E) crystallizing and is characterized in that: an ultrafiltration manner is adopted to filter when the filtration is carried out in the step (B), the extracted solution is firstly filtered by using a 100-500 kD ultrafiltration membrane and then is filtered by using a 5-10 kD ultrafiltration membrane, and the average membrane fluxes are respectively controlled at 100-190 LMH and 20-24 LMH. According to the method provided by the invention, the steps of extraction and ultrafiltration are adopted in coordination with the processes of adsorption, decolorization, crystallization and the like, the content of the obtained salicin can reach 99.0%, the yield is high, the cost is low, and the water and a small amount of alcohol which are used in production can be recycled, so that the cost is lowered, the pollution to the environment caused by organic solvents is reduced, and the implementation of industrialization is facilitated.