The invention discloses a longan water soluble active substance, a method for extracting the same and application thereof in preparing the health care food with immunoregulation function. The extraction method comprises: (1) grinding; (2) enzymolysis; (3) enzyme killing, filtering and concentration; (4) preparation; and (5) drying. The longan water soluble active substance, the method for extracting the same and application thereof have the advantages of high extraction efficiency, mild reaction condition and economy and environmental protection, and improves the added value of longan, and promotes the deep processing of the longan industry.