<P>A novel magnetic carbon-based solid acid catalyst (C350-Cl) was synthesized through a simple impregnation-carbonization process and used for the pretreatment of corncob in an aqueous medium. Under the optimized pretreatment reaction conditions, the yield of pentose reached 91.6% with a hemicellulose removal rate of 91.7%, and the subsequent enzymatic digestibility of the pretreated corncob residue reached 90.0% at 48 h. C350-Cl is a magnetic enzyme-mimetic solid acid catalyst, and its catalytic behavior is similar to those of enzymes. In addition, the catalyst is also an excellent carrier for Fe and Cl in that the Fe<SUP>3+</SUP> and Cl<SUP>-</SUP>can be released slowly in the pretreatment to assist the hydrolysis of lignocellulose. Compared with the traditional method with other catalysts, this hydrolysis process is suitable for the effective and sustainable saccharification of lignocellulose for producing fermentable sugar.</P><BR>[FIG OMISSION]</BR>