Abstract: The key progresses in processing and apparat us of polyester industrial yarn production were reviewed in the light of structu re controlling during the formation processes according to the relationships of s tructure-properties-processing.The controlling on intrinsic viscosity of raw m aterial,the irregularities of undrawn yarn, the orientation and crystalline s tructure of the undrawn and the yarn during the drawing process was illustrated in detail.The irregularity of yarn was characterized by three means at least,w hich include the mass variations of yarn,the filament diameter variations of the cross-section of yarn,and the orientation and crystallinity variations of each filament cross-section.