The invention discloses an iron-based coating material for heat insulating protection and a coating preparation method thereof and belongs to the technical field of surface coatings. Raw materials selected include alloy blocks and pure metal blocks, and specifically are ferroboron, ferroniobium, ferrosilicon, pure chromium and pure iron; a high-temperature nitrogen gas atomizing method is adopted to prepare alloy powder, and the alloy powder of 20-45 um in degree of sphericity and granularity; a hypersonic flame spraying method is adopted to prepare an iron-based noncrystalline or nanocrystalline coating. The coating prepared by the method has relatively low heat conductivity and can be used for heat insulating protection of heat-end parts of automobile engines.