In this paper, the development and properties of floating bead insulation mortar were introduced. Based on the experimental study, a new kind of exterior wall external thermal insulating mortar had been successfully produced. For this material, fly ash floating bead and expanded pearlite which was modified by hydrophobe were taken as the lightweight aggregate, meanwhile, Portland cement was used as the inorganic binder, also the fiber and polymer were taken as the additive. The results of experiments indicated that properties of fly ash floating bead insulating mortar, such as thermal insulation, strength, crack resistant and climate resistant, were superior to those of expanded pearlite insulating mortar. On the other hand, other properties, such as bulk stability, aging resistant, climate resistant, crack resistant and fireproofing, construction workability were much better than those of expanded polystyrene sheet ( EPS) insulating mortar.