The liquefaction of cornstalk in the presence of polyhydric alcohols with sulfuric acid as catalyst was investigated. Effects of various liquefaction condition parameters on the liquefaction and its liquefied products were mainly investigated. Results showed that the liquefaction parameters had an obvious effect on the residue percent and the viscosity, acid and hydroxyl number of its liquefied products. The efficient liquefaction of cornstalk with low residue percent of 9.4% was obtained under the mild condition of a PEG #400/glycerin ratio of 7/3, a cornstalk/liquefaction reagent ratio of 1/5, a reaction temperature of 150°C, a reaction time of 30 min and a sulfuric acid amount of 4%, respectively. Under this condition, the viscosity, acid number and hydroxyl number of its liquefied products was 1430 cP, 18.5 mg KOH/g and 362.1 mg KOH/g, respectively.