The Crystallinity, orientation, crystallite size, yield stress and initital modulus of wet drawn PET filaments annealed at various temperatures and time intervals were measured by wide angle X-ray diffraction method and, stress strain curves. The following results were found; 1) The crystallinity increases as annealing temperature rises and time increases. In the case of 14$0^{circ}C$, 16$0^{circ}C$, and 18$0^{circ}C$, crystallinity increases up to 50% at 15 minutes of annealing, and there is nosignificant increase between the intervals of 15 and 30 minutes, whereas a remarkable increase(60%) is noted in the case of 22$0^{circ}C$. 2) The crystallite size of 010 plane and orientation(1/ $frac{1}{2}$) was observed when annealed at 20$0^{circ}C$. 3) Initial moduli increase with temperature rises and time increases and change almost linearly with crystallinities and orientations.