The invention discloses a method for preparing regenerated disperse dye easy-to-dye polyester through a waste polyester alcoholysis method. The method comprises: 1) pre-treating waste polyester; 2) carrying out alcoholysis on the waste polyester; 3) carrying out quality control on an esterified product, and adding a polyethylene glycol or polyethylene glycol adipate copolymerization monomer; and 4) carrying out condensation polymerization, and preparing slices, wherein the finally obtained regenerated disperse dye easy-to-dye polyester has the intrinsic viscosity of 0.60-0.70 dl/g, the meltingpoint of 220-240 DEG C, the diethylene glycol content of 3.0+/-0.3%, and the chromaticity b value of less than 8. According to the present invention, the prepared regenerated disperse dye easy-to-dyepolyester can be used for preparing disperse dye easy-to-dye polyester filaments and staple fibers, and can achieve the high-value recycling of waste polyester.