Wool powder was produced from wool fiber after pretreated with 0.5% NaClO solution and then it was cut into short pieces and ground with a special designed machine. Scanning electron microscopy (SEM) photos showed that super-fine wool powder around 2 mum can be produced from the fibers around 25 mum in diameter, and most of the powder was in the form of needle. FTIR analysis showed the absorbing peak around 1700 cm(-1) became sharp as the powder particle size decreased. X-ray diffraction analysis results showed that there was no evident changes in X-ray pattern when the fiber became powder particle, however, the crystallinity decreased in some degree as the particle size decreased. Thermal analysis results showed that the temperature for moisture evaporation in the powder was elevated to around 150 degreesC from 120 degreesC of the control wool fiber. As the powder particle size decreased, the temperature corresponding to the crystal cleavage and the destroying of the crosslinkages increased. The thermal analysis results showed that as the powder particle size decreased, the thermal stability increased slightly. (C) 2004 Elsevier B.V. All rights reserved.