In this study, we explored the transport laws and influence mechanisms of engineered nanoparticles (NPs) in saturated porous medium, focusing on the effects of biofilms and soil minerals on the transport of NPs and the underlying mechanisms. The results showed that there are significant differences in the transmission efficiencies of NPs with different types or sizes in the clean quartz sand medium. For NPs of different types, the transmission efficiency was in the order of ZnO>CeO₂>Fe₂O₃. For CeO₂ NPs between 20~100 nm, the increase of particle size would facilitate their transport in saturated porous medium. The enhanced ionic strength of the solution would inhibit the transport of ZnO NPs in the saturated porous medium, and the increased concentration of NPs would not benefit their transport. The traditional DLVO theory could well explain the transport of NPs in the uncoated saturated porous medium. Both biofilms and soil minerals could inhibit the transport of nanoparticles in saturated porous medium, via the adsorption to NPs by biofilms and the hetero-aggregation between minerals and NPs. Non-DLVO interactions as well as surface characteristics of the coatings contribute greatly to the enhancement of nanoparticle deposition.