Abstract: Rice straw is naturally covered by a thin layer of aliphatic hydrocarbon and inorganic substances, which prevents urea formaldehyde (UF) resin from penetrating into straw body and producing strong adhesion. The change law of rice straw interfacial properties was revealed by treating the rice straw surface with oxygen cold plasma for 3—7 min at 10—20 Pa and 100—350 W, and analyzing the sample before and after plasma modification with Xray photoelectron spectroscopy (XPS). The results showed that plasma could effectively etch and graft some new functional groups on the rice straw surface. After plasma treatment the content of carbon atom was significantly decreased and the content of oxygen atom was obviously increased on the surface of rice straw. It was helpful for wetting and permeating of the straw surface by urea formaldehyde resin when the C—C/C—H nonpolar bonds were remarkably reduced and the polar functional groups carbonyl and carboxyl were significantly increased on the straw surface after treatment with oxygen cold plasma. It was found from XPS analysis that the rice straw surface layer was covered with an inner sublayer of mineral substances and outer aliphatic hydrocarbon substances.