Four　kinds　of　co-composite　matters　including　alginate,　agar,　calcium　carbonate　and　activated　carbon　were　mixed　with　polyvinyl　alcohol　(PVA)　for　immobilizing　the　manganese-oxidizing　bacteria.　The　internal　structure　of　the　PVA　gel　beads　was　tested　and　analyzed　by　scanning　electron　microscope.　A　dense　layer　exists　in　the　surface　of　PVA　gel　beads　with　an　unequal　distribution,　and　adding　agar　is　useful　for　overcoming　this　shortcoming　and　increasing　the　number　of　internal　pore.　Adding　calcium　carbonate　decreases　the　diameter　of　the　gel　beads　and　improves　the　thickness　of　the　internal　pore　wall.　The　solution　and　expansion　of　PVA　beads　may　be　worsen　after　adding　sodium　alginate　and　agar　and　better　with　activated　carbon　and　calcium　carbonate.　All　the　four　kinds　of　co-composite　matters　are　useful　for　improving　the　mechanical　strength　of　the　PVA　gel　beads　until　the　ratio　is　lower　than　1%.　Activated　carbon　and　calcium　carbonate　relate　with　the　improving　of　the　bioactivity　and　mechanical　strength,　respectively.