The invention belongs to the field of plant extraction, relates to a reed high-added-value utilization technology, and in particular, relates to a method for preparing furfural and co-producing a fiberboard by extracting xylose through reed steam explosion. The method comprises the following steps: 1) fracturing and cutting raw material reeds into sections; 2) removing impurities; 3) carrying outsteam explosion treatment, and washing the treated material with water; 4) feeding a water washing liquid into a fractionating tower, collecting an aqueous solution containing formic acid, acetic acidand furfural from the tower top, and separating the formic acid, acetic acid and furfural aqueous solution by electrodialysis; and obtaining a reducing sugar mixture at the tower bottom; 5) adding yeast, fermenting, and then performing microfiltration to remove glucose to obtain a mixed solution containing xylose and arabinose; 6) performing reverse osmosis membrane concentration; and 7) preparing furfural, and preparing the fiberboard from remaining matters. According to the method, pentosan in the raw material reed is degraded into xylose through steam explosion without adding acid, water extraction is adopted for recycling, acid pollution is avoided, and economic benefits are obvious; the obtained xylose aqueous solution is used for producing furfural through a solvent method, the yield is high, steam is saved, and pollution is small.