High-temperature heat treatment may cause degradation of wood chemical components.Chemical composition changes on surfaces of the szemao pine wood(Pinus kesiya var.langbianensis)and alder birch wood(Betula alnoides)before and after heat treatment were investigated through X-ray photoelectron spectroscopy(XPS).The obtained results were as follows:(1)The O/C(oxygen/carbon)ratios of wood surfaces reduced evidently after the high-temperature heat treatment; this reduction indicated a decrease in oxygen-containing functional groups on the wood surfaces.(2)Contributions of C1(i.e.,carbon atoms bonded to carbon or hydrogen atoms)of the wood surfaces increased,whereas that of C2(i.e.,carbon atoms bonded to one oxygen atom)decreased after thermo-vacuum treatment(TVT)and superheated steam heat treatment(SSHT).Results also indicated that the relative lignin content increased and the hydroxyl group(-OH)of cellulose and hemicellulose decreased.(3)The ratio of O2(i.e.,oxygen atoms bonded to carbon atoms with a double bond,C=O)to O1(i.e.,oxygen atoms bonded to carbon atoms with a single bond,C-O)increased significantly; thus,the carbonyl groups(C=O)of lignin increased.(4)The changes in chemical compositions caused a significant equilibrium moisture content(EMC)reduction in the adsorption process.