PEN fibers of two different molecular weights. low and high, were prepared by high-speed melt spinning. The fine structure and physical properties of PEN fibers were investigated with various techniques such as wide-angle X-ray diffraction, birefringence, density. DSC, dynamic viscoelasticity, and tensile testing. From the WAXD test, PEN fibers of high molecular weight was found to have a reflection peak associated with orientation-induced crystallization that started to appear at take up velocities above 3km/min. In this region, the crystalline structure was dominated by $eta$ form crystal. This tendency was also confirmed by DSC thermogram, density, and birefringence data. In the DSC thermograms, the melting peak shifted to higher temperature with increasing take-up velocity, while the area of cold crystallization peak decreased. Especially, the temperature of melting peak increased remarkably with increasing take-up velocity in the range of 2$65^{circ}C$ to 298$^{circ}C$ for PEN fibers of high molecular weight. Mechnaical properties of the two PEN fibers were relatively improved by the high-speed melt spinning at higher spinning speeds. However, the initial modulus and tenacity of PEN fibers of high molecular weight decreased slightly at the take-up velocity of 7km/min.