Abstract: The quality effect of xonotlite-type calcium silicate thermal insulation materials by adding small amount of dicalcium silicate was studied.The basic raw materials were natural powder quartz and nature lime.The experimental result shows that the drying shringage of the themal insulation materials decreases rapidly as the adding amount of C₂S increases.When the adding amount of C₂S increases from 0 to 5%,the drying shrinkage of the samples decrease from 2.19% to 0.92%,the products become up-to-standard from its originally below the standard.The reason for the decrease of the drying shrinkage is that the adding of C₂S promoted the formation of the secondary grains.