The invention relates to a porous super-soft
polyester fiber FDY and a preparation method thereof. The porous super-soft
polyester fiber FDY is obtained by
spinning modified
polyester with a porous spinneret plate; spinneret pores in the porous spinneret plate are arranged in an oval shape, in other words, the centers of the spinneret pores are located on concentric ovals, and the concentric ovals are a series of ovals with the long axes collinear and the short axes collinear. The porous super-soft polyester
fiber FDY is obtained by carrying out metering, extruding, cooling, oiling, stretching,
heat setting and winding on modified polyester chips. The preparation method of modified polyester includes the steps that
terephthalic acid and ethanediol react to obtain
ethylene glycol terephthalate, dihydric
alcohol terephthalate obtained after
terephthalic acid and hexanediol containing branched chains react is added, the substances continue to react, and modified polyester is obtained. The fiber obtained with the method is good in performance, wherein the
linear density deviation rate is smaller than or equal to 0.5%, the
breaking strength CV value is smaller than or equal to 4.0%, the breaking elongation CV value is smaller than or equal to 8.0%, and the
yarn unevenness CV is smaller than or equal to 2.0%.