The invention discloses a polypeptide compound and a preparation method and application thereof. The polypeptide compound has a structural formula as follows: (X A X B X C X D X E -X) 2 KY, or {(X A X B X C X D X E -X) 2 K} 2 KY, or {({X A X B X C X D X E -X} 2 K) 2 K} 2 KY, where, X A is a polar amino acid molecule, X B and X E are alkaline amino acid molecules (the same or different), X C and X D are non-polar amino acid molecules (the same or different), K is lysine (Lys, K), and X and Y are 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.
