Liquefaction is a thermochemical conversion used to derive value-added chemicals from lignocellulosic biomass. The objective of this study was to understand the changes in the chemical and anatomical structures of biomass in the liquefaction process, which contributes to the discovery of a selective reaction pathway for the formation of high-quality liquefied products that can benefit downstream upgrading processes. The results showed that the decomposition of hemicellulose and lignin started at about 120 degrees C, leading to the formation of five-carbon sugars and phenolics. The decomposition temperature of crystalline cellulose was about 180-200 degrees C in our presented conditions, leading to the destruction of crystallized microfibrils. The analysis results suggest that the liquefaction of the plant cell wall possibly starts from the surface of the plant cell wall and works its way toward the center of the S2 layer. This study provides an approach to integrate the liquefaction process of the whole lignocellulosic biomass for value-added chemicals including monosaccharides and phenolic compounds.