Two different organic compounds with a same terminal group octadecyl were used to prepare two kinds of hydrophobic organic ultrathin films on the surface of Mg–Mn–Ce alloy. The OTS film was prepared by self-assembling of the n-octadecyltrichlorosilane (OTS), and STN film was prepared by polymer-plating of another octadecyl compound 6-stearylamino-1,3,5-triazine-2,4-dithiol monosodium (STN). The surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning probe microscopy, and contact angle meter. The results showed that the adhesion force at nano scale was reduced from 12.35 nN for substrate to 5.76 nN for STN film and 4.12 nN for OTS film. Besides, the nano friction force and coefficient also effectively reduced by modification of STN and OTS film on Mg–Mn–Ce alloy. Thus, hydrophobic organic films provide an effective approach to solve nano-tribological issues. Furthermore, it was also found that the differences of the friction properties between the two films were attributed to the structure of the head groups bonded to the substrate.