Sponge　iron　is　a　potential　material　for　nitrogen　and　phosphate　removal.　To　explore　the　performances　and　mechanisms　of　nitrogen　and　phosphate　removal　by　sponge　iron,　a　sponge　iron　biofilter　was　established.　The　results　showed　that　nitrate　was　completely　removed　at　HRT　of　48　h　without　external　carbon　source　and　at　HRT　of　3　h　with　C/N　ratio　of　5.　Furthermore,　it　was　easy　to　achieve　partial　denitrification　at　HRT　of　1　h　with　C/N　ratio　of　3.　The　mechanisms　of　nitrate　removal　were　chemical　reduction　and　nitrate　dependent　ferrous　oxidation　without　external　carbon　source　and　heterotrophic　denitrification　with　external　carbon　source.　XPS　result　indicated　that　phosphate　was　removed　by　the　formation　of　ferric　phosphate　precipitation.　High　throughput　sequencing　showed　that　iron-oxidizing　bacteria　Gallionellaceae　was　highly　enriched　in　biofilter,　accounting　for　17.83%,　which　indicated　that　it　was　feasible　to　achieve　autotrophic　nitrate　removal　by　sponge　iron　biofilter.