Abstract: A high-efficiency petroleum-degrading strain,Z1a-B,was isolated from the petroleum-polluted soil in Shengli Oil Field at Dongying,Shandong.By analyzing the morphology and cultural characteristics,Strain Z1a-B was identified as Albosporus in Streptomyces.Strain Z1a-B was tested to be quite strong in hemolyzing and petro-degrading activity,which implied that it was quite high in ability to produce biosurfactant.GC-MS analysis showed that the strain could almost completely degrade C12-C43 n-alkyl benzene and was also good at degrading dodecyl-benzene,phenanthrene,methyl phenanthrene,and naphthalene.To culture the strain,solid medium composed of 2 g of bran,40 g of chicken manure,52.5 g of peat and 1.5 g of quick-lime,or of 2 g of bran,20 g of rice,28 g of soy meal and 1.5 g of quick-lime is optimal.In the medium,Streptomyces grows quickly and vigorously and yields plenty of spores.It was found in the laboratory test that in soils when w（crude oil） was 10%,the strain reduced the crude oil in the soil by 67.5% after 50 days of incubation（35 ℃,pH 6.5）.

Key words: petroleum degradation, biosurfactant, screening, Streptomyces spp