【Objective】Pollution by Polycyclic Aromatic Hydrocarbons(PAHs)in the soil environment has become a serious problem. In recent years, microbial degradation of PAHs to achieve soil remediation has become an important method. However, microbial degradation is not a very efficient and ideal process for the remediation of PAHs-polluted environments. In this study, humic acid(HA)was added during the degradation process to explore its effect on the microbial degradation of PAHs. 【Method】Using pyrene as a typical PAH and HA as representative dissolved organic matter, Mycobacterium sp. NJS-1 with high pyrene degradation efficiency was selected to degrade pyrene with or without HA. Fourier transform cyclotron resonance mass spectrometry(FT-ICR-MS), laser confocal microscopy(CLSM), and techniques such as infrared and Raman spectroscopies were used to analyze the residual characteristics of pyrene, intermediates and colony changes during degradation.【Result】Results show: 1)The presence of HA significantly accelerated pyrene biodegradation. Approximately 88.33%±3.40% of pyrene was biodegraded within 7 days of incubation with the addition of HA, but only 35.33%±3.27% was biodegraded without HA; 2)The FT-ICR-MS results indicated that addition of HA induced two biodegradation pathways - attacking of 1, 2-positions and 4, 5-positions of pyrene by dioxygenase, whereas in the absence of HA only the 4, 5-position was attacked; 3)The CLSM results showed that HA enhanced the growth of Mycobacterium sp. NJS-1 with no death of bacteria cells. Simultaneously, tyrosine proteins and fulvic acid-like compounds under visible light were detected and showed that HA enhanced bacterial activity by biofilm formation; 4)The results of the spectral analysis showed that a series of bands, mainly including protein amide, tyrosine, tryptophan and phenylalanine, red-shifted, implying that the interacted forces from the functional groups of bacterial surfaces changed in the presence of HA.【Conclusion】HA can improve the degradation efficiency by increasing the degradation pathway of pyrene and inducing the interaction of functional groups on the cell surface to form a microbial membrane. Meanwhile, the addition of exogenous HA could also promote the interactions among colonies and accelerate the degradation.