In this study, the differences of structure and properties development during stabilization and carbonization between highly oriented and partially oriented polyethylene precursors were investigated. The effect of stabilization temperatures, time, and tension on the conversion process was studied using thermal analysis such as differential scanning calorimetry and thermogravimetric analysis, scanning electron microscopy, and single filament mechanical properties. Comparison of the resultant carbon fibers from these two kinds of precursor fibers showed that using partially oriented polyethylene precursor may reduce the stabilization time and temperature, with a diffusion-controlled process of sulfonation for stabilization. The mechanical properties of the resultant carbon fibers were evaluated.