The invention relates to a super-bright polyester partially oriented yarn and a preparation method thereof. The preparation method comprises the following steps: uniformly mixing terephthalic acid, ethylene glycol, dihydric alcohol containing silicon on a main chain, a fluorine-containing binary acid, 2,2,3,4,5,5-hexamethyl-3,4-hexanediol and doped modified ZrO2 powder, sequentially carrying out an esterification reaction and a condensation polymerization reaction so as to prepare modified polyester; and preparing modified polyester POY yarns from the modified polyester melt according to a POYprocess by adopting a triangular spinneret plate, thereby obtaining the super-bright polyester partially oriented yarn. The prepared super-bright polyester partially oriented yarn is high in dye-uptake, K/S value and color fastness during dyeing, and the national degradation speed is high. According to the addition of the 2,2,3,4,5,5-hexamethyl-3,4-hexanediol and the dihydric alcohol containing silicon on the main chain, the dyeing property of fibers is improved, and due to the addition of the fluorine-containing binary acid and the doped modified ZrO2 powder, the degradation performance of the polyester is improved; and the prepared product is excellent in dyeing property and degradation property.