Influence　of　Zn,　Mg　and　Cu　elements　on　mechanical　properties　and　hot　cracking　tendencies　of　cast　Al-Zn-Mg-Cu　alloys　were　investigated　by　using　orthogonal　experiment　method.　The　results　show　that　the　influence　of　three　elements　on　the　tensile　strength　and　hot　cracking　tendency　of　alloys　is　distinct.　The　influencing　sequence　on　the　tensile　strength　is　as　follows:　Zn　＞　Mg　＞　Cu,　while　the　order　of　affecting　hot　cracking　tendency　is　Cu=Mg　＞　Zn.　In　the　experiment　range,　tensile　strength　and　hot　crack　tendency　are　increased　with　increasing　in　Zn　content,　and　decreased　with　increasing　in　Cu　content,　respectively.　However,　with　Mg　content　increases,　tensile　strength　shows　firstly　increased　and　then　decreased,　while　hot　crack　tendency　shows　firstly　decreased　and　then　increased.　The　eutectic　phase　with　low　melting　point　and　along　the　grain　boundary　has　important　effect　on　tensile　strength　and　hot　cracking,　where　with　the　eutectic　number　increases,　tensile　strength　is　decreased,　and　hot　tearing　tendency　is　firstly　reduced　and　then　increased.