Abstract: The mechanical properties,sintering behavior and toughening mechanism of ZrO₂-Al₂O₃ composite ceramics are investigated.The results show that the preferential flexural strength and fracture toughness can be obtained when ZrO₂ content is in the range of 10%-30%.It is also indicated that ZrO₂ particles can hinder the movement of grain boundaries,accelerate densification and improve microstructures.Furthermore,the toughening mechanisms include transformation toughening and crack inflection toughening.Besides,Dislocation is fixated by ZrO₂ nanoparticles,which blocks cracks of sample,so the toughness of material is unproved.