The lightweight of refractories used for steel ladles is of great significance for energy saving and reduction of the specific refractory consumption per ton of steel. In this paper, the erosion mechanisms of alumina magnesia carbon refractories containing lightweight alumina aggregates in the impact zone of 170 t steel ladle bottom were investigated, and the comparison with traditional dense alumina magnesia carbon refractories was analyzed. The results show that the alumina magnesia carbon refractories using lightweight alumina aggregates exhibit a better application effect. The wear rate decreases from the original 1.79 mm/heat to 1.35 mm/heat, and the service life increases by nearly 24.6%. It is found that the introduction of lightweight alumina aggregates with high surface roughness and abundant micro-sized pores can not only strengthen the bonding interface between aggregates and matrix, but also absorb the thermal stress through pores, which contributes to the improved erosion resistance and thermal shock resistance of alumina magnesia carbon refractories. It also promotes the formation of a thick dense calcium hexaluminate and MgAl₂O₄ spinel composite isolation layer at the hot face, which impedes the slag corrosion and penetration as well as oxidation of carbon. In addition, slag can be absorbed by the lightweight alumina aggregates and a special core-shell structure formed, and thus better slag corrosion resistance is obtained.