The invention discloses a high-shrinkage cation normal-pressure easy-to-dye polyester chip and a preparation method thereof. The high-shrinkage cation normal-pressure easy-to-dye polyester chip comprises the following components: 66-68 percent of purified terephthalic acid, 23-21 percent of glycol, 3.2-5.5 percent of isophthalic acid digylcol ester-5-sodium sulfonate, 2.1-3.3 percent of polyethylene glycol, 0.5-0.7 percent of isophthalic acid, 3.1-4 percent of hexanedioic acid, 0.012-0.036 percent of antimony acetate and 0.005-0.055 percent of antioxidant. The high-shrinkage cation normal-pressure easy-to-dye polyester chip is subjected to an esterification reaction at the pressure of 0.25-0.3MPa and the temperature of 250-260DEG C and a polycondensation reaction at the temperature of 230-270DEG C and at the vacuum degree of 0.08-0.098MPa and temperature preservation after the temperature reaches 272-278DEG C. The high-shrinkage cation normal-pressure easy-to-dye polyester chip has the advantages of high dyeing rate and dye suction rate at normal temperature and normal pressure, bright color, favorable performances of high shrinkage and resisting pilling, spinnability, drafting property and favorable physical property and post treatment performance of fibers.