In order to increase the stability of magnetite nanoparticles (MNPs) in suspensions and enhance their transport in the porous media,carboxymethyl cellulose (CMC) was used to modify MNPs.Batch experiments were conducted to investigate the stability of bare MNPs and CMC-modified MNPs in the artificial groundwater (AGW).Influence of CMC on MNPs transport in the quartz sand was also studied by using 1-D column experiments.The increase of surface charge due to CMC modification inhibited agglomeration of MNPs,and thus increased the stability of MNPs in the CMC solution.Such effects also greatly promoted the transport of MNPs in the quartz sand.