Iridium is the most promising material due to its high melting point and good chemical inertness, which is one of the most potential high-temperature oxidation-resistant materials for refractory metals above 1800 oC in aerospace filed. In this paper, the impendence and necessity of the iridium coating on refractory metals were introduced. The properties of iridium were presented in detail. The deposition methods and applications of the iridium coating from American, Japan, Europe and China were reviewed. Further, the advantages of double glow plasma technology and microstructure of the iridium coating produced by double glow plasma on refractory metals were highlighted in this study.