The　effect　of　the　addition　of　CaO-MgO-SiO2　glass　on　the　sintering　and　mechanical　properties　of　Al2O3/3Y-TZP　composites,　was　investigated.　The　higher　mechanical　properties　of　Al　2O3/3Y-TZP　composites　are　mainly　associated　with　the　stress-induced　transformation　toughening　and　microcrack　toughening.　The　fracture　toughness　measurement　was　carried　out　on　the　polished　surface　by　microindentation　method　using　Shetty＇s　equation.　The　microstructure　of　the　sintered　bodies　was　observed　by　scanning　electron　microscopy　(SEM)　on　the　polished　and　thermally　etched　surfaces.　The　finer　grain　microstructure　as　well　as　higher　content　of　t-ZrO2　was　benefited　to　the　improvement　of　mechanical　properties.　It　was　found　that　the　densification　of　alumina　was　enhanced　by　the　addition　of　TiO2-Mn2,　and　the　microstructure　development　was　characterized　by　their　promotion　to　the　grain　growth.