Microstructure,　tensile　strength　and　hot　cracking　tendencies　of　cast　Al-7Zn-2.5Mg-Cu　alloy　with　Al-5Ti-B　grain　refiner　contents　including　0,　0.2%,　0.5%,　0.8%　and　1.2%　were　investigated.　The　results　show　that　grains　of　Al-7Zn-2.5Mg-Cu　alloy　are　refined　obviously　by　adding　Al-5Ti-B　grain　refiner.　With　increasing　in　the　refiner　addition,　the　grain　size　is　decreased　firstly　and　then　slightly　increased.　The　smallest　grain　size　with　66　μm　can　be　observed　with　0.8%　grain　refiner.　As　grain　size　decreases,　the　number　of　eutectic　is　increased,　resulting　in　the　improvement　of　tensile　strength　and　decrease　of　hot　cracking　tendencies　of　cast　Al-7Zn-2.5Mg-Cu　alloy.　Tensile　strength　and　grain　dimension　follow　the　relationship　of　σb　=　47.22711　+　1325.35477　×　d-1/2,　and　hot　cracking　tendencies　and　grain　dimension　follow　the　relationship　of　H　=　41.73912　+　0.5733　×　d.　Eutectic　phase　also　affects　the　tensile　strength　and　hot　cracking　tendency　of　the　alloy.　Under　experimental　conditions,　tensile　strength　is　decreased　and　hot　cracking　tendency　is　decreased　firstly　and　then　raised　with　increasing　in　the　eutectic　number.