Fractionation of fibrous fraction from steam-exploded rice straw (SERS) of high moisture content have been studied with respect to the separation degree of fibrous tissue from non-fibrous tissue including epidermal, parenchymatous and vessel tissue using a fluidized bed opposed jet mill. Chemical composition and fiber characteristics, such as fiber size and composed cell proportion were studied for the separated fibrous fraction of SERS. 70.4% high cellulose fibrous fraction with 63.1% fiber cell content and 65.6% cellulose content was produced from the fractionation process. The separation degree of fibrous tissue of the fractionated fibrous fraction was 2.04. The mean fiber length was 0.97 mm, slightly longer than the untreated rice straw. The new method is suitable to produce high fiber tissue content fractions without damaging the raw fibers extensively. (c) 2006 Published by Elsevier Ltd.