With the industrialization process all over the world,problems that energy consume too fast and serious energy crisis have appeared.The use of heat insulation refractory is one of the main factors to reduce the industrial furnace energy.Heat insulation material which is nearer to the work layer has the better insulation.Two parts of work were done in this paper.Firstly,in order to prepare a kind of high performance microporous aggregate used for the alumina-magnesia castable in ladle lining,with a-Al2O3 micro-powder as mam raw material,microporous corundum aggregate was prepared by the method of wet grinding.The distribution of pore size,thermal conductivity and microstructure of microporous corundum aggregate were tested by means of mercury porosimetry,Laserflash thermal analyzer,scanning electron microscopy,etc.The results show that : ①there are large numbers of pores in microporous corundum aggregate,these pores inside distribute uniformly,the internal corundum grains grow well and the crystals are short columnar;②when compared to the ordinary tabular corundum aggregate,the closed porosity of microporous corundum aggregate is higher,apparent porosity is lower,and bulk density is lower,moreover,pores inside it are smaller;③ when the thermal conductivity of aggregates are compared,microporous corundum aggregate is significantly lower than that of ordinary tabular corundum ( bulk density of it is 3.63 g/cm-3),it is 42% less.Secondly,lightweight alumina-magnesia castable was obtained using this microporous corundum aggregate,fused magnesia powder and corundum powder as main raw materials.In terms of alumina-magnesia castable,the sintering properties,strength after baking and heat treatment at different temperatures,thermal conductivity coefficient and resistance to slag were tested in the experiment.The results show that : ①when compared with the ordinary alumina magnesia castable which is made of tabular alumina,lightweight castable has lower linear change rate,greater apparent porosity and smaller bulk density.Strength of it after baking and medium temperature heat treatment can reach the requirements in industrial production,however,the strength of it improves obviously after I 500℃ heat treatment;②when the thermal conductivity of castables are compared,thermal conductivity of two kinds of castables are basically the same in 350℃,when the test temperature rise to 600C and 800℃,thermal conductivity of lightweight castable made by microporous corundum aggregate is lower significantly;③when the resistance to slag are compared,two kinds of castables have basically same the corrosion index,the penetration index of lightweight alumina-magnesia castable is 14.3% bigger.