Considering　the　quality　of　secondary　effluent,　the　denitrification　filter　was　utilized　to　treat　the　urban　secondary　effluent.　By　comparing　the　nitrogen　removal　of　the　filter　under　different　C/N　and　filtration　rates,　the　appropriate　operating　parameters　of　the　filter　are　obtained,　therefore　providing　technical　support　for　transformation　of　the　plants.　When　the　C/N　equals　4.42　and　filtration　rate　is　3.4　m/h,　the　denitrification　filter＇s　removal　is　proved　to　be　optimal,　with　TN　less　than　5　mg/L　in　the　effluent　and　low　content　of　NO3--N　and　NO2--N.　By　monitoring　the　denitrification　filter　along　the　way,　nitrogen　removal　was　mainly　concentrated　on　the　water-side　front　700　mm,　ultimately　determining　1300　mm　as　the　best　filter　layer　height.