Petroleum, one of the main energy resources, plays an important role in the progress of human culture. With the development of petroleum industry, soil contamination by petroleum products has become a worldwide environment problem. This study investigated the effects of inoculation using microorganism, identified as an arbuscular mycorrhizal fungus (AMF), Glomus intraradices on oat under petroleum stress using a pot experiment in greenhouse. The concentration of petroleum in the tested soils was 5000mg/kg. The results showed that the degradation rate of the total petroleum hydrocarbons (TPHs) of the inoculation treatments was significantly higher than the non-inoculation group. By detection the index of plant growth and physiology, such as soluble protein and MDA, the results showed that all the inoculation treatments increased plant tolerance to the TPHs stress and which could promote the phytoremediation.