The biodegradation of phenanthrene was investigated in the liquid phase by gram-negative bacteria Sphingobium sp. PHE3 immobilized on montmorillonite, goethite and maize straw-derived biochar. The results of scanning electron microscopy showed that there was the largest number of bacteria adhered to the surface of the biochar with the best morphology. The addition of montmorillonite and biochar significantly (P<0.05) improved the degradation rate of phenanthrene by microorganisms, as well as the increase of polysaccharide and protein production in bacterial extracellular polymeric substance (EPS). Nevertheless, there was no obvious effect on phenanthrene biodegradation and EPS production with the addition of goethite. Furthermore, quorum sensing might play a role in biofilm formation. The signal molecules C8-HSL and C12-HSL secreted by PHE3 might mediate the production of EPS and phenanthrene biodegradation to some extent.