The invention relates to a porous superfine denier flat
yarn and a preparation method thereof. Modified
polyester is spun by a porous spinneret plate to prepare the porous superfine denier flat
yarn; the arrangement form of spinneret holes in the porous spinneret plate is in an
ellipse, namely that the hole center of each spinneret hole is positioned on concentric ellipses, the concentric ellipses are a series of ellipses, the long axes of all the ellipses are collinear, and the short axes of all the ellipses are collinear. The modified
polyester is subjected to
slicing,
solid-phase polycondensation and
viscosity increasing, so as to prepare the porous superfine denier flat
yarn. A preparation method of the modified
polyester comprises the following steps of reacting
terephthalic acid and
ethylene glycol to prepare
ethylene terephthalate; adding
ethylene terephthalate prepared by reaction of
terephthalic acid and
branch chain-containing
ethylene glycol, and continuously reacting, so as to prepare the ethylene terephthalate; continuing to react, so as to obtain the modified polyester. The porous superfine denier flat yarn has the advantages that the prepared
fiber property is excellent; the
linear density deviation is smaller than or equal to 0.5%, a break strength CV (
coefficient of variation) value is smaller than or equal to 4.0%, a break elongation CV value is smaller than or equal to 8.0%, and a yarn unevenness CV value is smaller than or equal to 2.0%.