"Poly(trimethylene terephthalate) (PTT) shape memory fabrics" have excellent shape recoverability, whose clothes are easy to take care. In order to study the mechanism of “PTT shape memory fabric"’s shape recoverability, test of removing yarns from fabrics and comparing their crease recoveries with those of fabrics was designed. Results showed that crease recovery ratios of "PTT shape memory fabrics" were about 36%, while those of yarns removed from them were nearly 80%. Therefore, the results revealed that PTT yarns had good recoverability, however, the high inter-filament frictional forces in the fabric offerring by tight weave structures prevented PTT yarns from recovering. When the applied force was large enough to overcome frictions between filaments, the fabric gained sufficient mobility, coupled with PTT filaments’ excellent elastic recovery properties, and gave excellent fabric crease recovery. Moreover, new test method was designed independently to test different kinds of yarns’ crease recovery angles, results had proved once more PTT yarns had good elastic recovery, and their crease recovery ratios were close those of wool yarns, while the crease recovery of natural silk and cotton were the worst.