NOVELTY - Pseudomonas psychrophila Den-03 (I) preserved in China microbial culture collection management committee general microbial center on March, 27 2012, and under preservation number of CGMCC No. 5941, is new    USE - (I) is useful for treating urban sewage by denitrification (claimed).    ADVANTAGE - (I) ensures the stable denitrification efficiency with low temperature, improves the denitrification of the winter urban sewage treatment system, improves the production efficiency and reduces the production consumption.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for the screening (I) comprising taking 10 ml of fresh activated sludge from harbin urban sewage treatment plant and then adding into the aerobic denitrifying medium triangular flask of 100 ml, then putting into the swing bed at a temperature of 10 degrees C for 48 hours and rotating at a speed of 150 revolutions per minute to obtain the enrich bacterium liquid, taking 10 ml of enriched bacterium liquid and then adding into the aerobic denitrifying medium triangular flask of 100 ml, repeating the culture condition to obtain the domestication bacterium liquid, taking 100 mu l of domestication bacterium liquid into solid aerobic denitrifying medium plate, coating them evenly by the coating method, putting them into a incubator at a temperature of 10 degrees C and then culturing for 48-72 hours to obtain the single bacterial colony and then repeating for 3-4 times, where the aerobic denitrifying medium comprises 7.9 g/l of disodium hydrogen phosphate heptahydrate, 0.3 g/l of ammonium chloride, 4.7 g/l of sodium citrate, 1.5 g/l of potassium hydrogen phosphate, 0.1 g/l of magnesium sulfate heptahydrate and 1.5 g/l of potassium nitrate, dissolving 2 ml of trace element liquid into 1000 ml of distilled water and adjusting the pH value of 5.2, where the trace element liquid comprises 50 g/l of EDTA, 2.2 g/l of zinc sulfate, 5.5 g/l of calcium chloride, 5 g/l of manganese chloride tetrahydrate, 5 g/l of ferrous sulfate heptahydrate, 1.1 g/l of ammonium heptamolybdate, 1.57 g/l of copper sulfate pentahydrate, and 1.61 g/l of cobalt chloride hexahydrate and the pH value of 7.2.