The methods to reduce the distortion of ceramic fiber rigid insulation tiles during high temperature firing procedure required for coating forming were studied. The results indicate that the distortion of the tiles is caused by compressive stresses in coating. However, the distortion significantly decreases when only the coated surface of the substrate is fired at high temperature or a thicker substrate is employed during coating forming and then machined to the required final thickness. And a further decrease of the distortion is achieved when these two methods are used at the same time. Moreover, the distortion decreases with the increasing thickness of substrates independent of the method used.