Corrosion of five corundum-mullite refractories with the different porous aggregates and the same matrix by the blast furnaceslag was conducted using the static crucible test. Effects of properties of corundum-mullite aggregates on the slag resistanceof refractories were investigated through X-ray diffractometer (XRD), scanning electron microscopy (SEM), and mercuryporosimetry measurement, etc. It is found that the porous corundum-mullite aggregates have different slag absorbing capacity,which affects the composition of the corroded aggregates and matrices at slag/refractory interface, and thus affects the slagcorrosion and penetration resistances. Comparing with the dense corundum-mullite refractory, the porous corundum-mulliteaggregate with 31.6% apparent porosity (AP) substituting the dense aggregates in the refractories does not make the slagresistance degenerate and reduces the bulk density by 16.7 wt%; whereas, when the APs of aggregates increase to 41.6-44.8%,the slag resistance sharply deceases. It is a successful case that the developed lightweight refractory with high slag resistancehas a potential application for working lining of high-temperature furnace.