Abstract:This paper introduced the mechanism of microbial degradation PAHs in the soil, compared the different degradation metabolic processes for phenanthrene by Bacillus sp. and Mycobacterium sp., analyzed the metabolic processes for phenanthrene and pyrene by M.vanbaalenii PYR-1, stated that the degradation for PAHs by microbial oxidation mainly begin from K- and Bay- region, and the degradation of the toxic PAHs is mainly attributed to the oxidation of K- region. Fungi have stronger degradation ability to the benzo[a]pyrene comparing to bacteria. Also this paper gave the proposed pathways for phenanthrene, pyrene and benzo[a]pyrene for the further research.