The　technology　core　of　biological　removal　of　iron　and　manganese　by　contact　oxidation　is　iron　and　manganese　oxidizing　bacteria.　This　article　made　a　study　on　down　flow　and　up　flow　filtration,　the　results　show　that　down　flow　filtration　of　the　homogenous　filter　medium　is　more　adapted　to　the　reproduction　of　biotic　formation.　Homogeneous　filter　increase　the　depth　of　effective　biological　filter　and　the　biomass　that　develop　the　bio-chemical　capability　of　the　biological　filter.　Homogeneous　filter　increase　removal　capability　of　Fe/Mn　and　alleviate　the　formation　of　sludge　cake,　which　can　get　a　quite　backwash.　Down　flow　homogeneous　biological　filter　can　solve　some　engineering　problems　of　heterogeneous　up　flow　filtration.　The　down　flow　homogeneous　biological　filter　is　more　adapted　to　the　removal　of　Fe/Mn　in　groundwater.