AbstractMercerized fibers were prepared from native cotton fabrics via NaOH solution treatment at different concentrations. . In addition, the cotton fibers were converted into a swollen and rough state after mercerization treatment. The results of Fourier transform infrared spectrometry and wide-angle X-ray diffraction indicated that the cellulose molecular structure changed (e.g. the degree of disorder of O-H stretching vibration increased, while the crystallinity index decreased) in the process of mercerization. Thermogravimetric analysis determined that the cellulose II fibers were more thermally stable than the cellulose I fibers. The mechanical properties of cellulose fiber-reinforced polyethylene oxide (PEO) composites showed that both original and mercerized cotton fibers enhanced the tensile strength of the PEO matrix. These properties directly contributed to the advantages of mercerized textile products (e.g. higher luster, holds more dye, more effectively absorbs perspiration, and tougher under different washing conditions).