The present invention discloses a polypeptide compound, a preparation method and an application thereof. The structural formula of the polypeptide compound is (XAXBXCXDXEXFXG-X)2KY or {(XAXBXCXDXEXFXG-X)2K}2KY or {({XAXBXCXDXEXEXG-X}2K)2K}2KY where, XA, XB, XD, XE and XG are one of aliphatic amino acid molecules respectively, XC and XF are aliphatic amino acid molecules or heterocyclic amino acid molecules, K is lysine (Lys, K), X or Y is null or any one or more amino acid or chemical groups. The polypeptide compound provided in the invention has an effect of enhancing the immune function of a body and has an application potential of being developed into a clinical medicine capable of enhancing the immune function of a body.
