Ceramic fiberboard generally has a density of 280-550. When used as a heat insulation layer, the density is generally 280-350. Because there is no need to see fire, the strength requirement is not too high, and this density is also the density with the best heat insulation performance. If the density is higher or lower, the heat insulation performance will decrease. For refractory layer, the density should be appropriately increased with the temperature requirement to improve the service life, but it is not necessary to choose too large density, on the one hand, the density is too high, will make the thermal conductivity increased, resulting in lower insulation performance, on the other hand, the density is too high, will lead to ceramic fiber board hardness increased, but will be more likely to crack, so according to the use of conditions of reasonable selection of product density.