Halide-activated pack cementation and Air plasma spraying methods were utilized to deposit Si-modified MCrAlY coatings. Nb-base alloys were coated with MCrAlY by Air plasma spraying and followed by pack siliconizing process at 1100°C for 8h and 10h. The pack powders were consisted of 5 Wt.℅NH4Cl、35 Wt.℅Si、60 Wt.℅Al2O3. Si-modified MCrAlY coatings have three-layer microstructure. The outer layer was composed of NbSi2 and Nb3Ni2.4Cr1.6Si6, while the middle layer comprised the compound of Nb、Ti、Ni、Cr、Si. The inner layer adjacent to the substrate was silicide. Isothermal oxidation resistance of Si-modified MCrAlY coatings was tested at 1250°C in static air. Si-modified MCrAlY coatings had excellent oxidation resistance, because continuous Cr2O3 and SiO2 scales which serve as obstacle of oxygen diffusion were formed after oxidation.