Abstract The study of tritium permeation barrier (TPB) coating is one of the most important subjects in the development of liquid lithium blankets in ITER and future fusion reactors. Erbium oxide ceramic is a promising candidate material for a TPB coating because of its high electrical resistance and high compatibility with liquid lithium. In this paper, an Er 2O 3 coating was fabricated by using a magnetron sputtering method to deposit it on a China Low Activation Martensitic (CLAM) steel substrate. Er was performed as the buffer in order to improve the adhesive property of the Er 2O 3 ceramic. The crystallinity of the coating was observed by X-ray diffraction (XRD) after annealing. A dominant orientation (4 4 0) presented with a thickness more than 1.5 μm. The structural properties, surface morphology and other physical properties of the coating were also studied.