The invention discloses a method for extracting beta-lactoglobulin from milk, which comprises the following steps: 1) carrying out first centrifugation on fresh milk so as to obtain skim milk; 2) carrying out second centrifugation on the skim milk so as to obtain whey, and carrying out ultrafiltration on the whey so as to obtain a first permeate; 3) adding a mixture of retinal and ethyl acetate into the first permeate, and carrying out filter pressing on the obtained mixture by using a first plate-and-frame filter press so as to obtain a first retentate; 4) dissolving the first retentate in a sodium hydroxide solution, and carrying out filter pressing on the obtained object by using a second plate-and-frame filter press so as to obtain a second retentate, adjusting the pH value of the second retentate by using hydrochloric acid, so that the pH value of the second retentate is 4-6, and passing the second retentate through a nanofiltration membrane under the action of second pressure, so that a third retentate is obtained; and 5) rinsing and drying the third retentate, so that the beta-lactoglobulin is obtained. The method disclosed by the invention solves the technical problem that the beta-lactoglobulin is not easily extracted.