Abstract: To study the unevenness on the surface of PTT/PET plain knitted fabric, seamless knitted fabrics with PTT/PET were woven on trial basis. The “random strip unevenness” which couldn’t be eliminated by technical adjustments on the surface of PTT/PET plain fabrics was analyzed by studying the original configuration of PTT/PET and the configuration of PTT/PET after simulated finishing process. It was found that the three-dimensional endless spiral crimps of PTT/PET is the cause of “random strip unevenness”. Based on this, a new kind of PTT/PET filaments was made by improving the spinning process. The “random strip unevenness” was disappeared on the surface of knitted fabric made of the new PTT/PET filaments, and it appears uniform and aesthetic.