The invention discloses a culture medium for improving the speed of nitrifying bacteria oxidizing nitrites. The composition of the culture medium is that every 1000 milliliters of water contain 2.1 to3.1 grams of glycerin, 1.3 to 1.9 grams of yeast extract, 1.0 to 2.0 grams of baking soda,1.9 to 3.2 grams of sodium nitrite, 0.1 to 0.8 grams of sodium carbonate, 0.1 to 0.5 grams of sodium chloride, 0.1 to 0.5 grams of potassium dihydrogen phosphate, 0.1 to 0.5 grams of magnesium sulfate and 0.005 to 0.05 grams of ferrous sulfate, wherein the glycerin and the yeast extract are better to be supplemented at the late stage of fermentation. The culture medium ensures obvious promotion of the speed of growth metabolism of the nitrifying bacteria and significant increasing of the degradation rate of the nitrites, thereby the average degradation rate of the invention is increased 40% to 127% in comparison with a conventional culture medium 900-1320mgNO2-N/gMLSS.d. Tests of small water body and real water body prove that bacteria cultured by the invention can continuously and high effectively degrade nitrites in polluted water body.