Abstract: The effects of thermal-mechanical treatment on surface characteristics of straw were investigated by means of infrared （IR） and X-ray photoelectron spectroscopy （XPS） analysis. Results showed that there are great differences in chemical composition between outer face and inner face of rice straw. For example, there are only a few active groups, like hydroxyls, on outer face of the straw with an oxygen/carbon （O/C） ratio as low as 0. 068 while more hydroxyl groups were on the inner face where the O/C ratio reached 0. 284. However, after thermal-mechanical treatment, more hydroxyl groups occurred on the straw fibers obtained by thermal-mechanical treatment and the O/C ratio increased greatly. The results indicated that thermal-mechanical treatment can improve interface bonding efficiency between straw and adhesives. It provides evidence for further study on manufacturing straw-based MDF with UF resin.