The　start-up　of　ANAMMOX　bio-filter　for　domestic　secondary　effluent　was　investigated　in　ambient　temperature.　The　raw　water　for　ANAMMOX　bio-filter　was　the　effluent　from　an　anoxic-aerobic　(A/O)　phosphorous　removal　system.　Nitrification　biofilm　was　successfully　transformed　into　ANAMMOX　biofilm　during　7　months,　with　the　induction　of　added　nitrite,　hydrazine　and　oxyammonia.　The　highest　TN　removal　rate　reached　6.8　kg/m(3)/d　during　start-up,　with　observed　growth　rate　of　0.0018　h(-1)　and　doubling　time　of　16.45　d.