The invention relates to a preparation technology of a soybean protein concentrate by an ultrasonic continuous countercurrent leaching alcohol method, comprising the following steps of: (1) sieving low-temperature defatted soy flour by using a 20 mesh sieve to remove foam and transporting oversize materials into a presoaker for presoaking 15-30min at normal temperature; (2) transporting the presoaked soy flour into an ultrasonic continuous countercurrent leaching device for extracting, wherein extractive alcohol concentration is 65-80 percent, a material solution ratio is 1:5-1:8, an ultrasonic frequency range is 20-100KHz, ultrasonic power is 100-500W, leaching temperature maintains 25-40 DEG C, and leaching time is 30-90min; (3) firstly carrying out pre-exsolution of the leached proteinwet flour by an extruder, then, entering a flash evaporation desolventiser to carry out exsolution at exsolution temperature of 45-60 DEG C, and drying products subject to exsolution and crashing into 100 meshes to prepare finished products; (4) recovering alcohol from the leached alcohol leaching liquid by using a flash film concentrator, meanwhile, concentrating to obtain soybean molasses withsolid concentration of 45-55 percent; and (5) recovering soybean isoflavone from the leached alcohol leaching liquid, wherein the with yield of soybean isoflavone reaches 2-4 mg/g. The invention has simple preparation and very remarkable effect.