Ferrous　micro-beads　from　fly-ash　were　used　as　starting　material　to　prepare　CoZn-Z　type　barium　ferrite.　As　the　main　impurity　in　the　beads,　SiO2　plays　an　important　role　on　the　electromagnetic　properties　of　the　ferrites.　To　investigate　the　effect　of　SiO2　content,　a　series　of　CoZn-Z　type　ferrites　with　various　contents　of　SiO2　(1　wt%,　2　wt%　and　5　wt　%)　were　prepared　with　analytical　pure　Fe2O3　and　SiO2.　The　density,　phase　composition,　microstructure　and　electromagnetic　properties　of　the　sintered　samples　were　investigated.　The　results　show　that　the　permeability　of　samples　alters　little　at　a　low　content　of　SiO2　about　1　wt%,　but　deteriorates　dramatically　when　the　addition　of　SiO2　is　above　2　wt%.　The　ferrous　micro-beads　were　then　treated　by　alkali　cleaning　to　reduce　the　content　of　SiO2　to　about　1　wt%,　and　the　samples　prepared　with　these　treated　beads　show　a　similar　performance　on　the　electromagnetic　properties　with　pure　CoZn-Z　type　ferrite.