Nine species of biomass with different lignin contents were liquefied by water in an autoclave at noncatalytic and catalytic runs. The absolute values of the correlation coefficients between the lignin content and the oil and the char yields were about 0.898 for non- catalytic aqueous liquefaction and 0.883 for catalytic aqueous liquefaction, indicating a strong correletion. With both processes of aqueous liquefaction, with increasing lignin content, the oil yield decreased, and the char yield increased.