The refractory and insulation coating material is composed of 50-90 wt% inorganic fiber, 5-40wt% cement, 0.2-15wt% gypsum, 0.2-1wt% polysaccharide, 0.2-0.8wt% condensation product of naphthalene sulfonic acid and formaldehyde, and 0.2-2wt% polyvinyl alcohol or methyl cellulose. The application method comprises (A) uniformly mixing above coating composition except inorganic fiber with water of 1.9-3 times the amount of the composition to make slurry binder and (B) separately spraying 50-90wt% inorganic fiber together with the slurry so that they contact with each other crossedly and adhere to the surface of structure to be coated.