Routine analyses and new biotechnologies,such as sole carbon source utilization tests (Biolog),were applied to investigate changes in physico-chemical properties and microbial ecology of petroleum contaminated soil,Results show that petroleum contamination did not affect much soil hydrolysable N,total N,total P,available K and total K.But the observed increases in soil organic matter and decreases in soil pH,might have led to changes in microbial ecology of the soil,Although there was no significant difference found between the clean and the contaminated soils in numbers of cultivable heterotrophic bacteria and actinomycetes,hydrocarbon-degraders and PAHs-degraders in the contaminated soil were about 100 to.000 times higher in number than in the clean soil,Community level physiological profile using Biolog sole carbon source utilization tests was used to investigate effect of petroleum on soil microbial diversity.Diversity indices,such as Gini index,McIntosh index,and McIntosh evenness,increased in the contaminated soil,The above results indicate that petroleum contamination increased microbial diversity of the soil,Besides,the acute bio-toxicity test by the luminous bacteria method showed that the DCM/DMSO extract from the petroleum contaminated soil is toxic to the bacteria and only.950 μ g ml^-1 in EC50.