The　recycling　and　utilization　of　plastic　resources　from　waste　toner　cartridges　in　printers　is　an　inevitable　trend　for　sustainable　social　development.　However,　the　environmental　health　risks　caused　by　residual　toner　microplastics　inside　the　cartridges　limit　the　regeneration　treatment　of　waste　toner　cartridges.　This　study　focused　on　the　harmless　treatment　of　toner　microplastics　in　waste　toner　cartridges　and　the　resource　utilization　of　polystyrene　shell　plastics.　Through　in-depth　analysis　of　their　microstructure　and　composition　characteristics,　a　harmless　treatment　method　based　on　pre-melting　technology　was　proposed.　The　experimental　results　indicated　that　225　°C　was　the　critical　upper　limit　temperature　for　the　pre-melting　and　agglomeration　of　toner　microplastics,　which　could　effectively　achieve　their　stabilization　and　harmless　treatment.　Meanwhile,　a　multi-stage　purification　process　route　was　designed　and　implemented　for　polystyrene　plastic　in　waste　toner　cartridges,　which　included　key　steps　such　as　pre-melting,　magnetic　separation,　saltwater　flotation,　and　extrusion　granulation,　successfully　achieving　efficient　regeneration　of　polystyrene　plastic.　Further　heat　transfer　simulations　revealed　that　the　presence　of　Fe3O4　particles　significantly　promoted　heat　transfer　within　the　toner　polymer,　providing　a　theoretical　basis　for　optimizing　the　pre-melting　process.　In　addition,　based　on　large-scale　data　statistical　analysis,　the　system　evaluated　the　physical　stability　and　safety　of　recycled　polystyrene　plastic,　verified　the　feasibility　and　practicality　of　this　treatment　technology.　This　study　achieved　the　elimination　of　diffusion　hazard　of　toner　microplastics　while　recycling　polystyrene　plastic　from　waste　toner　cartridges.　©　2025　Elsevier　Ltd.