The article is to review the research process and application of amino acid fragments used as carrier in nanometer drug delivery system.The poly-amino acid carrier is mainly applied as pH-sensitive carrier,micelles-forming carrier and gene therapy carrier.pH-or temperature-sensitive carrier Water-soluble methoxy poly(ethylene glycol)-block-dendritic poly(1-lysine) MPEG-block-DPL4 with 4 generation PLL was synthesized by liquid-phase synthesis with well-defined structure.