To clarify liquefaction ratios and their construction variations of the main chemical compositions of wood in phenol using phosphoric acid as a catalyst, the chemical ingredients of wood such as holocellulose, cellulose and lignin, were measured and extracted according to GB methods. With Fourier transform infrared (FTIR), the product identification of reactant before and after liquefaction in phenol was investigated. The molecular weights and their distributions of the liquefaction results (acetone soluble parts) were studied by gel permeation chromatography (GPC). Results show that the molecular weights and their distributions of poplar and Chinese fir are almost the same. In poplar, the distribution of cellulose is the largest, and that of holocellulose the smallest after liquefaction. For Chinese fir, the distribution of holocellulose is the largest, and that of cellulose the smallest. After liquefaction of poplar cellulose, the change bands of FTIR spectrum observed below 1 600 cm-1, can be attributed to new substitute groups. The same is true for poplar lignin. For Chinese fir, the spectra of liquefaction results of all chemical compositions differ from that of wood meal. This reveals the more activity groups were produced because of the reactions between Chinese fir and phenol. The research shows that the liquefaction ratios of poplar decrease in the following order: holocellulose ＞ lignin ＞ cellulose, and those of Chinese fir in the order: lignin ＞ cellulose ＞ holocellulose.