The experiment studied on the rhizosphere effect in phytoremediation of the petroleum polluted soil by three kinds of grasses which were Pannicum， Eleusine indica(L.) Gaerth and Tall Fescue. After a period of 150 d ,this pot experiment show that the three kinds of plants rhizosphere accelerated the degradation of petroleum in different degrees.The results show that the plant roots improved the soil moisture which increased 5% compared with unplanted control soil .The dehydrogenas activity is 0.61～1.20 times higher.The number of microorganisms in the rhizosphere increased three orders of magnitude.The abduction of plant rhizosphere environment and the coercion of petroleum changed the distribution and activity of microorganisms.The petroleum degradation rates in the rhizosphere are 22.1%～30.3% higher than in the unplanted control soil.The effect of rhizosphere degeneration changed the component of petroleum obviously.It strengthened the degeneration degree of normal hydrocarbons that had low and moderate carbon.The plant rhizosphere environment is favorable to degenerate the high-carbon hydrocarbons into the low-carbon hydrocarbons.At the same time the peak area ratios of Pr/nC₁₇,Ph/nC^₁₈ and Pr/Ph have been enhanced 0.99,2.69 and 1.25 respectively.It accelerated the isomerization of normal hydrocarbons.

Phytoremediation, Rhizosphere, Microbial numbers, Dehydrogenas activity, Hydrocarbon degeneration