High-entropy multicomponent oxide coatings have emerged as a promising material due to the enhanced elemental miscibility and glass forming ability. This chapter designed and fabricated ZrNbCrAlSiO coatings for the protection of zirconium alloys. After surface hypoxic treatment, the formation of (Zr, Nb, Cr, Al)M–O–Si mixed bonds on the surface enhances the structural stability of (ZNCA)1S3 at subcritical environment. At 1000 ℃, a stable high-entropy amorphous nanocrystalline structure was formed in (ZNCA)1S3, significantly reduces the grain coarsening, alleviates stress induced by high-temperature oxidation, and minimizes surface cracking. ncbvncbvncbvnc