The invention relates to a method for quickly starting an oxygen-poor ammonia oxidizing biofilter, and relates to a method for biological denitrification of waste water, which comprises the following steps of: (1) inoculating an anaerobic denitrification biomembrane biofilter, and after a denitrification biomembrane is cultured, converting the anaerobic denitrification biomembrane biofilter into an oxygen-poor environment for cultivating oxygen-poor ammonia oxidizing bacteria; (2) taking inorganic carbon NaHCO3 as a carbon source, taking NH4Cl as a nitrogen source of ammonia nitrogen, taking NaNO2 as the nitrogen source of nitrite nitrogen, taking KH2PO4 as a phosphorus source, and controlling the pH value to be alkalescent, wherein the concentration is low-matrix, and the temperature is room temperature; adding hydroxylamine, and inducing and inoculating sludge to be converted towards an oxygen-poor ammonia oxidizing biomembrane; and (3) taking the biofilter as a reactor, and taking ceramsite as filter materials. In the method, the oxygen-poor ammonia oxidizing bacteria are applied to the sewage denitrifying technology to realize the shortest denitrification of nitrogen, so the problems of a large number of required carbon sources and neutralizers, large energy consumption and large sludge producing amount in the conventional biological denitrifying technology are solved.