General situation studying on new technology of biological nutrient removal is summarized, such as the principle of denitrifying dephosphataion and factors affecting it , such as pH, DO, SRT, MISS etc. The principle of simultaneous nitrification and denitrification and factors affecting it are given, such as carbon source, DO, the property of activated sludge ect. The principle of shortcut nitrification -denitrification and factors affecting it is also given such as temperature, pH, the concentration of ammonia, DO etc. The principle of anaerobic ammonium oxidation and factors affecting if is proposed such as stayer, pH, temperature etc. The technics and its peculiarity of these new technology of biological nutrient removal is commented.