The invention discloses a high-strength PET (polyethylene terephthalate) copolyester material for 3D printing and a preparation method thereof, and belongs to the field of a PET copolyester material. A specific amount of poly-L-lactic acid and poly-d-lactic acid are added; through the synergistic effect with a specific coupling agent, the mechanical strength of the material is improved; meanwhile, the shrinkage rate and the dimension stability of the 3D printing material are obviously improved. The degradable biological material is added in the material, so that the environment compatibility is good; the addition quantity of required reinforced fibers is little; the cost is low. The copolyester material provided by the invention is suitable for 3D printing.