High water absorption for thermal insulations will decrease thermal insulating and mechanical proper ties. In this paper,the effects of components on water absorption were investigated. Moreover,regarding to the problem of high water absorption,thermal treatment and hydrophobic nano鄄silica were adopted to solve the problem. The results indicates that nano鄄alumina and E鄄glass has little effect on water absorption of the composites,and water absorption will increase with the addition of zirconite. Heat treatment can decrease the water absorption to some extent,but should
be tightly controlled below 800益. The introduction of hydrophobic nano鄄silica can significantly decrease water absorp tion and shorten absorption balance time. Furthermore, better results can be achieved with the increase of additive a mount of hydrophobic nano鄄silica.