NOVELTY - Nitrobacter winogradskyi XY-01 with preservation number of CGMCC10171, is new.    USE - The strain and microbial inoculum are useful for degrading nitrite-nitrogen in water bodies, preferably aquaculture water (claimed).    ADVANTAGE - The strain: can screen sewage treatment plant activated sludge, and has strong nitrite degradation ability (claimed); can remove nitrite-nitrogen in culture farming water; solves nitrite accumulation problem in aquaculture water; and increases fish and shrimp production yield.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) culture medium for culturing the N. winogradskyi XY-01, comprising 1.7-3.2 g disodium phosphate, 0.18-0.36 g monopotassium phosphate, 0.3-3 g sodium nitrite, 0.01-0.03 g magnesium sulfate heptahydrate, 0.001-0.003 g calcium chloride, 1-20 ml ionic solution, and pH 7.3-9 in 1 l water, and added with 1.5% solid agar, where ionic solution comprises 1 g iron(ii) sulfate heptahydrate, 1 g EDTA, and 1 l water; (2) culturing the N. winogradskyi XY-01 using the culture medium, comprising culturing by using batch culture including using spectrophotometry to measure nitrite nitrogen concentration in nutrient solution, when the nitrite nitrogen concentration is lower than 30 mg/l, adding 40% sodium nitrite solution to the culture medium to maintain nitrite nitrogen concentration to 200-400 mg/l, and finishing culturing when the optical density of 600 (OD600) reaches more than 3; (3) use of the N. winogradskyi XY-01 in preparing water treatment microbial inoculum comprising a stabilizer and a protective agent; (4) preparing the microbial inoculum, comprising (a) concentrating the N. winogradskyi XY-01 fermentation liquid; and (b) adding the stabilizer and protective agent; (5) use of the microbial inoculum in degrading nitrite-nitrogen in water bodies, preferably aquaculture water; and (6) water treatment method, comprising placing N. winogradskyi XY-01 or microbial inoculum in water, which is rich in water nitrite.