Levoglucosan is served as a significant versatile product to generate high value-added chemicals and pharmaceutical additives. Levoglucosan was predominately produced from pyrolysate of cellulose. However, the direct fast pyrolysis of waste biomass produces a small quantity of levoglucosan in comparison with the theoretical value of cellulose. This study explored Fenton pretreatment as a possible route to enhance levoglucosan yield during the fast pyrolysis of the waste corncob. The experimental results showed that different Fenton pretreated conditions and pyrolytic temperatures played vital roles in the formation of levoglucosan. The levoglucosan yield from fast pyrolysis at 500 °C of corncob pretreated by Fenton reaction of 14 mL/g H2O2 and 16 mM FeSO4 was about 95% higher than that of the untreated corncob. Additionally, Fenton pretreated corncob was capable of obtaining the levoglucosan at a low pyrolytic temperature (300 °C). It was mainly attributed to the effective disrupting of biomass structures and the selective degradation of lignin and hemicellulose during pretreatment. Furthermore, the powerful removal of alkali and alkaline earth metals during Fenton pretreatment was beneficial to increasing the levoglucosan yield. These findings demonstrate that Fenton pretreatment can provide a novel effective method to enhance levoglucosan yield during biomass fast pyrolysis.