The present invention discloses a polypeptide compound, a method for preparing the polypeptide compound, and an application of the polypeptide compound. The polypeptide compound is represented by a structural formula A-(A-K)n-Y, n being a natural number； wherein A is a short peptide fragment with biological activity； K is lysine Fmoc-Lys (Dde)-OH that contains two active amino groups, and Y is null or any one or more amino acids or chemical groups； when n=1, the structural formula of the polypeptide compound is A-(A-K)-Y； when n=2, the structural formula of the polypeptide compound is A-(A-K)2-Y； when n=3, the structural formula of the polypeptide compound is A-(A-K)3-Y； . . . . The polypeptide compound disclosed and provided in the present invention has effects of inhibiting tumor growth and improving immune function.
