NOVELTY - Degrading oily sludge of well field by using micro-organism, comprises (i) culturing, separating, sieving, acclimating, and mutating to obtain Pseudomonas aeruginosa, Micrococcus luteus, Bacillus subtilis and Acinetobacter junii, and mixing; (ii) degrading; and (iiia) transferring the oily mud polluted to an oily mud processing bed reactor, flattening, irrigating, crushing, and adding an organic nitrogenous fertilizer and phosphorus fertilizer, (iiib) thinning, and processing, and (iiic) carrying out spot management, ventilating, and watering.    USE - The method is useful for degrading oily sludge of well field by using micro-organism.    ADVANTAGE - The method reduces the concentration of petroleum used in the processing system with mixed bacteria from 17215 mg/kg to 1257 mg/kg; has a degrading rate of 92.7%, petroleum substance removal rate of 89.1%, and good effect; and processes the oily sludge with an initial oil rate of 10.55% for 56 days.    DETAILED DESCRIPTION - Degrading oily sludge of well field by using micro-organism, comprises (i) culturing, separating, sieving, acclimating, and mutating the oily sludge of loess plateau to obtain Pseudomonas aeruginosa, Micrococcus luteus, Bacillus subtilis and Acinetobacter junii, and mixing to obtain the oily sludge degrading microbial flora according to the weight ratio of 1:1:1:1; (ii) degrading under proper condition, where the initial pH is 6, weight ratio of carbon to nitrogen is 100:3, weight ratio of carbon to phosphorus is 100:0.6, temperature is 30 degrees C, and the other conditions are not limited rigidly, and are provided by the natural condition of the loess plateau; and (iiia) transferring the oily mud polluted by spilled oil of the well field to an oily mud processing bed reactor, flattening, and irrigating after crushing, and adding an organic nitrogenous fertilizer and phosphorus fertilizer according to the degrading condition, (iiib) thinning the mixed degraded microbial flora, and adding to the oily sludge according to the initial concentration of 5 parts/million (ppm), where the bacterium applying period is for 20 days, and processing thrice, where the concentration of the second and third bacterium applying is 3 ppm, and (iiic) carrying out spot management by using a reactor to control the temperature of the processing system at 30 degrees C, applying bacterium and fertilizer primarily, and adding nitrogenous fertilizer and phosphorus fertilizer according to the proportion in an interval of 15 days, and plowing the soil of the reactor, ventilating, and watering in an interval of 5 days till the end of the processing stage.