The alumina-spinel refractory castables were prepared by using tabular alumina and spinel as main raw materials, calcium aluminate cement as binder, metallic Al powder (≤0.15mm) as additives. The anti-explosion temperature of castable samples was detected. The characteristics of microstructure, pore size distribution and air permeability were analyzed by techniques of SEM, Mercury Injection Apparatus and Pressure-difference Method respectively. The influence of Al powder on explosive spalling resistance of alumina–spinel castables were studied, and the pore formation mechanism and explosion-proof of Al powder in castables were investigated. The results showed that the anti-explosion temperature of alumina-spinel castables increased and then decreased with the increase of Al powder content, which is consistent with the changing tendency of the air permeability. During the curing of castable samples, the exothermic peak moved forward steadily with the increase of Al content; however, it moved forward significantly when Al powder content over 0.075%. Microstructure analysis showed that the number of pores increased significantly with the Al powder addition,it is found that the pore size of the castables increased with increase of Al powder addition.