In this paper, iridium coating was produced by double glow plasma on various substrates. Microstructure, mechanical property, thermal stability and ablation resistance of the iridium coating were investigated. The coating was the columnar grains with a preferred (220) orientation. The adhesive force of the coating on carbon substrate was smaller than that of the coating on the refractory metals and carbide. After heat treatment above 1400oC, many micropores appeared on the surface of the coating. The surface of the coating also presented micropores after ultrahigh temperature ablation. The iridium coating could endure the high temperature up to 2000oC and could protect the substrate from oxidation.