The liquefaction of cellulose in the presence of phenol without or with sulfuric acid as catalyst was investigated. The liquefied products were characterized by GC/MS and FTIR. Results showed that reaction temperature and reaction time had obvious effects on liquefaction of cellulose. Sulfuric acid showed an excellent catalytic degradation. The chemical compositions of the liquefied products produced using sulfuric acid catalyst or not were almost identical, and the majority of the identified liquefied products were methylene bisphenol and its isomers. During the process of liquefaction, the degradation of cellulose and condensation polymerization occurred at the same time. The last liquefied products were greatly dependent on the reaction conditions.