Geopolymer was prepared by Metakaolin (MK) stimulated by sodium silicate and sodium hydroxide. X-Ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize micro-structure of geopolymer and geopolymer based coating. A serial of reagents were added to modify the coating and a thermal insulation material was produced. It was revealed that MK has quasi-crystal structure and the produced geopolymers had amorphous structure. The surface of geopolymer based coating, as well as the compressive strength, adhesive strength with concrete, could be modified by adding a certain amount of silane coupling agent, mica powders and wollastonite. By mixing the asprepared geopolymer and hollow glass beads with a volume ratio of 4:1, a thermal inslation coating was produced, which had a promising application in the surface protection of hydropower dam.