Porous PTT (polytrimethylene terephthalate) fiber FDY (fully drawn yarn) and preparation method thereof

The invention relates to porous PTT (polytrimethylene terephthalate) fiber FDY (fully drawn yarn) and a preparation method thereof. The porous PTT fiber FDY is prepared from modified PTT through spinning by a porous spinneret plate; spinneret holes in the porous spinneret plate are arranged elliptically, that is, the centers of the spinneret holes are located on concentric ellipses which are a series of ellipses, major axes of the ellipses are collinear, and minor axes of the ellipses are collinear. The porous PTT fiber FDY is prepared from the modified PTT through processing; a preparation method of the modified PTT comprises the following steps: terephthalic acid and 1,3-propanediol react to prepare 1,3-propanediol terephthalate, terephthalic acid and diol containing branched chains are added for a reaction, diol terephthalate is prepared and continuously subjected to a reaction, and modified PTT is obtained. The prepared fiber has excellent performance, the linear density deviation is lower than or equal to 0.5%, the breaking strength CV value is lower than or equal to 4.0%, the breaking elongation CV value is lower than or equal to 8.0%, and the yarn unevenness CV is lower than or equal to 2.0.