Abstract: During the biodegradation of the hydrocarbons in polluted soils of the aeration zone,the nutrition level is a pivotal limiting factor.This paper showed that the bio-available N is 0.814 7 g/kg dry soil,and the bio-available P is 36.9 mg/kg dry soil,which are both seriously deficient for the biodegradation and cannot meet the need for the growth of the degrading microbes in the nature soil of the Zihe Valley.Experiment results indicated that the supply of oxygen by the tilling enforces the biodegradation,and according to analyses by the column-chromatography,degradation rates of the three hydrocarbon compounds are aromatic hydrocarbons>saturate hydrocarbons>colloid.