A green and efficient strategy for the hydrolysis of cellulose was developed by using a magnetic lignin-derived solid acid catalyst (MLC-SO3H) in the presence of ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl). The results indicated that reaction temperature, reaction time, catalyst loading and water content have a big influence on the yield of total reducing sugars (TRS). By optimizing these reaction parameters, 69.3% TRS yield was observed at 140 ℃ for 150 min with the addition of 40 wt% MLC-SO3H and 1 wt% water. More importantly, MLC-SO3H could be easily separated from the reaction mixture with an external magnet and could be repeatedly used five times without an obvious loss of catalytic activity, demonstrating that it possessed excellent recyclability. Furthermore, a plausible mechanism involving three consecutive processes of dissolution, adsorption and catalysis for the hydrolysis of cellulose in [BMIM]Cl over a catalyst of MLC-SO3H was also proposed.