The invention discloses a method for preparing polyacrylic acid-poly trimethylene carbonate-polylactic acid copolymer micelles. The method includes steps of 1), adding polyacrylic acid, hydroxyl-terminated polylactic acid mono-lauryl ether, solvents and condensing agents into reactors and carrying out reaction to obtain polyacrylic acid-polylactic acid graft copolymers; 2), adding the polyacrylic acid-polylactic acid graft copolymers, amino-terminated poly trimethylene carbonate mono-tridecyl ether, solvents and condensing agents into the reactors and carrying out reaction to obtain double-graft copolymers; 3), adding the double-graft copolymers and solvents into the reactors and dissolving the double-graft copolymers to obtain double-graft copolymer stock solution; 4), adding the double-graft copolymer stock solution into dialysis bags, placing the dialysis bags into beakers filled with selective solvents, carrying out displacement by 3-4 times, pouring the double-graft copolymer stock solution into volumetric flasks with scales, and regulating the double-graft copolymer stock solution until the double-graft copolymer stock solution reaches certain scales to obtain the polyacrylic acid-poly trimethylene carbonate-polylactic acid copolymer micelles which are aimed compounds. The method has the advantages that processes for preparing the polyacrylic acid-poly trimethylene carbonate-polylactic acid copolymer micelles are simple and are easy to master, and each aimed compound obtained by the aid of the method is a novel medicine carrier.