Abstract: Cerium isooctoxyborate (CeIOB) was prepared. The anti wear and friction reducing properties of cerium isooctoxyborate as an additive in oil were evaluated on an MS 800A four ball friction and wear tester and an HQ 1 friction and wear tester. The chemical states of B on the rubbed surface were determined by X ray photoelectron spectroscopy (XPS). The results indicate that CeIOB possesses excellent load bearing capacity and good anti wear and friction reducing properties. XPS analytical result indicates that CeO 2, B 2O 3 and Fe 2B exist in the rubbed surface of the steel. These reaction products contribute to improve the anti wear and friction reducing properties.