Composites　of　Al2O3　and　3%　(in　mole)　yttria-stabilized　tetragonal　zirconia　polycrystals　(3Y-TZP)　were　prepared　by　liquid　phase　sintering　with　the　addition　of　CaO-MgO-SiO2　glass　as　sintering　additive.　The　effects　of　the　sintering　additive　on　the　densification,　microstructure　and　mechanical　properties　of　the　composites　were　investigated.　The　results　indicate　that　the　densification　is　greatly　improved　by　the　addition　of　CaO-MgO-SiO2　glass　because　of　its　lower　liquid　viscosity.　The　composites　can　be　densified　at　1500°C.　The　average　grain　sizes　for　Al2O3　and　ZrO2　are　associated　with　the　sintering　temperature　and　the　composite　composition.　Some　grains　of　Al2O3　and　ZrO2　in　the　microstructure　are　intragranular.　The　sintering　temperature　is　reduced　after　the　introduction　of　CaO-MgO-SiO2　glass,　and　this　gives　the　composites　a　fine　grain　structure　and　excellent　mechanical　properties.　Bending　strength　of　778　MPa　is　obtained　under　the　optimal　preparation　conditions.