NOVELTY - For removing the nitrate nitrogen of sewage in low temperature, Rhodococcus sp. (2CGMCC No.5287) is used. It has the ability to remove the nitrate nitrogen of sewage in low temperature and aerobic condition.    USE - For removing the nitrate nitrogen of sewage in low temperature (claimed).    ADVANTAGE - The Rhodococcus sp (2CGMCC No.5287) removes the nitrate nitrogen of sewage in the low temperature, especially under the condition of 8-12 degrees C. Compared with the non-inoculated sewage, the sewage inoculating the Rhodococcus improves the removing rate for the nitrate nitrogen by 10%.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for separating culture method of the Rhodococcus for removing the nitrate nitrogen of sewage in low temperature, involving: (1) vaccinating the sludge (10-20 ml) of the aeration tank of the sewage treatment plant into the conical flask with nitric acid bacterial culture solution (250 ml), where the density of the nitrogen of the sodium nitrite in the nitric acid bacterial culture solution is 50 mg/l, rotating via the table with a rotating speed of 120-140 revolution per minute (rpm) under the temperature of 8-12 degrees C, domesticating in the table, keeping stay to the degradation rate of the nitrite nitrogen reaching 80-90%, removing the liquid supernatant, vaccinating the sludge at the bottom of the conical flask into the second nitric acid bacterial culture solution (250 ml), where the concentration of the nitrite nitrogen in the second nitric acid bacterial culture solution is 150 mg/l, rotating via the table with a rotating speed of 120-140 rpm under the temperature of 8-12 degrees C, domesticating in the table, keeping stay to the degradation rate of the nitrite nitrogen reaching 80-90% and then obtaining the nitric acid bacterial culture solution with anti-low temperature bacterium; (2) taking the culture solution (10 ml) obtained in the step 1), adding into the 250 ml conical flask with sterile purified water (90 ml) and 20-30 grains of sterilization glass bead, oscillating for 10-30 minutes, making the bacterium cell releasing fully on the liquid supernatant, keeping stay for 20-40 minutes, taking the liquid supernatant into the tube with the sterile purified water (9 ml), obtaining 10-2 of the bacteria suspension, processing serial dilution according to above method until 10-8; (3) selecting the bacteria suspension with gradient of 10-5 to 10-8, respectively taking vaccinate (1 ml) the solid medium of the nitrate bacteria, doing three parallel sample for each dilution, numbering and moisturizing cultivating for 2-3 weeks under the condition of 10 degrees C and aerobic condition; (4) selecting the single colony with big size and different form from the solid medium of the nitrate bacteria in step 3), streaking again in the solid medium of the nitrate bacteria flat, repeating flat streaking for 3-4 times, making the colony on the flat be with the same form, singleness and same size under the microscope, namely single colony, naming with nitrate-2, which is the Rhodococcus sp (2CGMCC No.5287) for removing the nitrate nitrogen of sewage in low temperature after identification.