Three strins,named as NS-1,NS-3 and NS-5,which could degradate oil effectively,were isolated from the oil-polluted soil in Northern Region of Shaanxi and the degradation effect was determined by the method of colourimetry.The results showed that NS-1 could make the oil degrade by 89.63% when the original concentration of oil was 4 g/L.The culture medium of NS-1 was optimized by minitab software by the way of PB testing,Box-Behnken center combination design and the response surface analysis based on the fermentation medium.It was indicated that MgSO4,(NH4)2SO4 and NaCl were key factors for NS-1 growth,and the optimal recipe of the culture medium was 2.0% glucose,0.9% MgSO4,0.1%(NH4)2SO4,0.4% NaCl,and the yield of NS-1 was increased by 38.7% after culturing for 20 h,compared to that with LB culture medium.