Abstract: The RF reactive sputtering method was used to deposit wear resistant chromium oxide coatings and the properties of the coatings were studied. The results showed that there existed two modes of sputtering during RF reactive sputtering, i.e., metal sputtering mode and nonmetal sputtering mode caused by the reaction between the target and reactive gas. The deposition rate was very low in the nonmetal sputtering mode. The hardness of chromium oxide coatings depends mainly on the content of Cr₂O₃ in the coatings and low hardness CrO will form when oxygen is not enough during sputtering. Feeding oxygen near the substrate is an efficient technology for depositing hard chromium oxide coatings at high deposition rate.