A pot experiment in greenhouse was carried out to investigate the interactive effects of arbuscular mycorrhizal fungi (AM) inoculation and PAHs-specific degrading bacteria (DB) inoculation on the phytoremediation of long-term PAHs contaminated soils. The results indicated that AM and DB inoculation promoted PAHs degradation in the soil with alfalfa (Medicago sativa L.). After 90 days, total PAHs content in soil reduced by 47.9% and 49.6% for the treatment of AM and DB respectively, but only by 21.7% for control. For the treatment of DB+AM, total PAHs content in soil reduced 60.1%, showing synergy effect of AM and DB inoculation. In addition, the average PAHs degradation gradually reduced with the increase of PAHs rings, but DB inoculation promoted the degradation of four-ring PAHs and five-ring PAHs. The removal ratio of PAHs from soil increased with the increases of the amount of culturable PAHs degrading microorganisms and the activity of dehydrogenase. Therefore arbuscular mycorrhizal fungi inoculation and PAHs-specific degrading bacteria inoculation were effective to the phytoremediation of long-term PAHs contaminated soils.