Abstract: Through incorporating different amount of fly ash (FA) and air entraining agent (AEA) to thermal insulating mortar blended with vitrified microsphere (VM),the influence of fly ash (FA) and air entraining agent (AEA) on properties like consistency,wet apparent density,dry apparent density,compressive strength and thermal conductivity of the thermal insulating mortar was investigated systematically. The results indicate that,when incorporating fly ash lonely,thermal insulating mortars consistency increased first and then reduced. However,wet apparent density,dry apparent density,compressive strength and thermal conductivity were all declined first and then rised,mortars drying shrinkage was inhibited to some extent simultaneously. Taking integrated performance of thermal insulating mortar into account,there exist optimal incorporating amount of AEA for the mortar mixing both FA and AEA. In addition,for thermal insulating mortar blended with VM,the properties were acceptable for incorporating 20 kg/m3 FA and 0. 1% AEA.