The friction and adhesion characteristics of the self-assembled film of octadecyltrime-thoxysilane (OTE SAM) on the surface of SiO2 under the relative humidity of 5%—99% were studied using atomic force microscopy/friction force microscopy(AFM/FFM). Experimental results indicate that OTE SAM can not only improve the tribological properties of SiO2 surface,but also show well anti-wear properties under the pressure of the load of 200nN, or Hertz pressure of 0.8GPa. Due to the strong hydrophilicity, the friction force between the FFM tipe and SiO2 surface increases with the relative humidity when it is lower than 50%HR and then decreases sharply. However, due to the well hydrophobe property of OTE SAM, the friction force between FFM tipe and the surface of OTE SAM is much lower than that of the FFM/SiO2 surface and slightly decrease with relative humidity. Therefore, OTE SAM will be a good boundary lubricant of high speed recording system.