The surface of wood/polyethylene(PE) composites was treated by silicane coupling agent to improve its adhesion properties. To explore the durability of the bonding joint in water， the Fourier transform infrared spectroscopy(FTIR) and X ray photoelectron spectroscopy(XPS) were employed in the water immersion experiment to investigate the effect of water on the surface properties of coating treated wood/PE composites. The results show that there is a chemical combination between silicane coupling agent and the surface of the composite after the coating treatment. With the immersion time extended, the new groups are not formed on the surface for the composite, but the chemical environment for the chemical elements on the surface is changed. The contents of —OH and the CO groups on the surface of wood/PE composites are increased, which is resulted from swelling of wood fiber within wood/PE composite caused by absorbing water. There exists a homeostasis of the bond forming and bond rupturing for silicane coupling agent on the surface of the composite. And the swelling of wood fiber within wood/PE composite caused by absorbing water could result in further changes of surface properties. And the changes would have a considerable effect on the durability of the bonding joint.