Abstract: PET fibers with nano-mineral particles were prepared by mixing nano-mineral particles with PET pellets and subsequent alkali weight reduction. SEM observation for the surface and cross section of the fibers showed that the mineral particles with a small size dispersed from the surface to the inner of the fibers, which had apparent microcellular structure. With the addition of nano-mineral particles, there was no change for the crystalline allomorphs of the PET fibers, but its crystallite size increased, moreover crystallinity and degree of orientation decreased. Compared with common PET fibers, the breaking strength of PET fibers with nano-mineral particles decreased, but its breaking elongation and work of rupture increased, especially its capability of transmitting moisture improved markedly whereas mass specific resistance reduced evidently.