The high yield hydrolysis of cellulose to glucose in water remains a challenge due to the limited acidity and contact with the substrate for sulfonated carbons. Here we report on a unique sulfonated mesoporous carbon fiber with optimized acidity, which was produced by pyrolysis of FeCl3-impregnated wipe fibers and subsequent acid treatment. The Brönsted acidity (especially for SO3H) is generated by sulfonation of a magnetic carbon fiber intermediate, while the Lewis acidity comes from small Fe3O4 nanoparticles and defects remain. The balanced Brönsted and Lewis acidity combined with hydrophilic functionalities was simultaneously adjusted by varying the Fe / Wipe fiber (WF) feed ratio and the pyrolysis temperature to change the porous structure of the final catalysts. As expected, the elaborately manufactured MCF-SO3H-20-500 (20% of the Fe / WF feed ratio and pyrolysis at 500 ° C) provides 66.0% of the glucose yield when cellulose is completely converted. This is the highest glucose yield that can be achieved by hydrolysing untreated cellulose in water over a sulfonated carbon catalyst. The optimized Brönsted and Lewis acidity is mainly responsible for the directional conversion of cellulose to glucose, and rich hydrophilic functionalities and a superior mesoporous structure of the catalyst facilitate cellulose contact and mass transfer. This investigation will open new avenues to develop high performance carbon acid catalysts for cellulose hydrolysis.