A　packed　column　experiment　was　carried　out　to　study　the　migration　process　of　modified　nano-zero-valent　iron　(nZVI)　in　porous　media　and　the　change　process　of　hydraulic　characteristics　of　porous　media.　In　view　of　the　complexity　of　the　migration　mechanism　of　modified　nZVI　in　porous　media,　an　unsteady　variable　parameter　mathematical　model　considering　the　effects　of　interception,　Brownian　diffusion,　gravity　settling　and　the　change　of　porous　media　properties　was　established.　By　fitting　the　model　with　the　experimental　data,　the　changes　of　various　mechanisms　in　the　experimental　process　were　studied.　The　results　show　that　the　higher　the　injection　flow　rate,　the　higher　the　concentration　at　the　outlet,　and　the　lower　the　injection　concentration,　the　higher　the　throughput.　The　distribution　of　iron　particles　in　porous　media　is　not　uniform,　the　maximum　at　the　entrance　and　the　lowest　at　the　exit.　The　model　fits　the　test　results　well　under　various　test　conditions.　The　model　analysis　shows　that　in　the　process　of　particle　injection,　the　particle　size　is　small　at　the　beginning,　and　the　particles　are　mainly　attached　to　the　surface　of　the　medium　due　to　Brownian　motion.　As　the　experiment　proceeds,　the　particle　size　increases,　the　Brownian　motion　effect　decreases,　but　the　interception　and　gravity　settlement　effect　strengthens.　In　addition,　during　the　whole　process,　the　porosity　of　the　medium　decreases　gradually,　and　the　probability　of　collision　between　particles　and　porous　media　increases,　which　leads　to　the　increase　of　the　deposition　rate　coefficient.