[Objective] This study aimed to identify the key bacteria during the microbial degradation of pyrene in the sediments from Bohai sea and the potential interactions among these bacteria. [Methods] We set up the microcosms system with pyrene as the sole carbon source, apllied the Illumina Hiseq 2500 to reveal the bacterial communities, and then predicted the bacterial ecological interactions using CCLasso algorithm. [Results] The concentration of pyrene decreased by (67.07±2.37)% after 30 days and meanwhile the structures of bacterial communities were distinctly changed. The significantly enriched population consisted of Alphaproteobacteria, Flavobacteriia and Planctomycetia, whereas the relative abundances of Deltaproteobacteria, Anaerolineae and Spirochaetes decreased. The microbial ecological network was constructed and composed of 29 nodes and 143 edges. The classified genera with relatively high degree values included Erythrobacter and Planctomyces. The strong associations were observed between the genus Erythrobacter and some unclassified genera affiliated to the family Flavobacteriaceae and the class Alphaproteobacteria. [Conclusion] It is possible to address scientific questions from the classic ecology to identify the key bacteria during the biodegradation of polycyclic aromatic hydrocarbons compounds by marine microbial ecological networks. Our study discovered close interactions among key bacteria represented by the genera Erythrobacter.