The　impact　fatigue　resistance　(IFR)　of　nine　groups　of　grinding　balls　60　mm　in　diameter　made　of　four　different　kinds　of　cast　iron　was　tested　on　a　ball-on-ball　test　machine.　The　free-drop　height　of　each　ball　was　4.2　m　and　the　maximum　impact　energy　was　35　J.　Results　showed　that:　(1)　high　chromium　cast　iron　with　a　small　amount　of　retained　austenite　had　the　best　IFR　(2)　with　increasing　amount　of　retained　austenite　the　IFR　decreased;　(3)　grinding　balls　with　austenitic,　sorbitic　or　tempered　sorbitic　matrices　had　excellent　IFR;　(4)　manganese　ductile　iron　had　the　worst　IFR　and　was　not　suitable　for　making　grinding　balls;　(5)　martensitic　ductile　iron　had　an　appropriate　IFR　owing　to　its　proper　combination　of　strength　and　toughness.