Acid-treated, alkali-treated and ball-milled rice straw was used as a substrate by Trichoderma reesei for cellulase production. Of the three pretreated straws, ball-milled straw provided the highest yield of cellulase, which was 1.3-fold higher than commercial cultures containing cellose. The FT-IR of the precipitate from rice straw with 70% ethanol showed an absorption peak typical of polysaccharides, while high pressure liquid chromatography assays of monosaccharide composition showed that glucose was the major component, while galactose, xylose, arabinose and fructose were present in much smaller quantities. The addition of soluble polysaccharide (SPS) derived from rice straw increased FPase activity by 1.5-fold and beta-glitcosidase activity by 2.3-fold, respectively, indicating the inductive effect of SPS upon cellulase production, especially upon the yield of beta-glucosidase. Ball milling influenced the molecular weight and monosaccharide composition of SPS and thus affected the performance of SPS in cellulase production. Finally, the crude enzymes produced in culture with SPS were used for saccharification and provided a 1.3-fold higher yield of glucose than that produced in culture without SPS. Our results indicate that SPS could represent a key factor in solving problems caused by the lack of beta-glucosidase activity in enzymes produced by Trichoderma reesei.