In this study, Betula dahurica wood powder was liquefied with polyethylene glycol and glycerin as the liquefying reagents and sulfuric acid as a catalyst to investigate chemical groups, crystallinity and microcosmic morphological characteristics of liquefied wood residues by FTIR, XRD and SEM, and the mechanism of condensation reaction was verified. The results showed: 1) the condensation reaction occurred after about 70 min within liquefying time of 180 min. 2) Comparing to wood powder, the absorption characteristic peaks of aromatic rings and methoxy groups from lignin at 1 500, 1 607 and 1 248 cm-1 disappeared, and the absorbing peak at 1 739 cm-1 from carbohydrates became obviously smaller for the liquefied wood residues during decomposed and condensed reactions. 3) The crystallinity of the residues increased in decomposed reaction; however in condensation reaction, it had an increasing trend after it kept constant for a period of time. 4) The blocky accumulation was found from microcosmic morphology of liquefied residue in condensation reaction.