The invention discloses a polypeptide chest enlargement essence cosmetic and a preparation method thereof. The cosmetic is rich in beauty polypeptide components and mainly comprises acetyl hexapeptide-38, growth-modulating peptide GHK, palmitoyl-pentapeptide-3, palmitoyl-oligopeptide, acetyl dipeptide-13, 2% carbomer 940, aloe extract, xanthan gum, glycerin, butanediol, hyaluronic acid, methylparaben, germall and water. The essence contains abundant active polypeptide components and supplements nutrients required by thymocyte, cell proliferation is promoted from different ways, and accordinglythe good chest enlargement effect is achieved. The cosmetic is good in safety, has no toxic or side effect and can be used for a long time.