Polypropylene　(PP)-based　polymers　are　environmentally　friendly　and　degradable　materials　that　make　them　attractive　alternatives　to　polyethylene　for　the　electrical　insulation　systems　of　power　cables　in　the　future.　To　enhance　the　insulation　performance　of　PP　and　to　impede　leakage　currents　through　the　material,　different　admixtures　are　utilized.　In　this　paper,　the　effect　of　nano-fillers　on　charge　transport　characteristics　in　PP　composites　under　DC　electric　fields　is　investigated　by　using　a　bipolar　charge　transport　model　accounting　for　mobile　and　trapped　electrons　and　holes　as　well　as　ionic　species.　The　model　was　validated　by　comparing　the　numerical　results　with　the　experimental　data.　The　dynamic　distributions　of　space　charge　densities　and　electric　field　in　PP　with　and　without　nano-fillers　are　analyzed　and　compared.　The　numerical　results　confirmed　that　0.5　phr　ZnO　nano-fillers　can　significantly　improve　the　electric　field　distribution　in　PP　nanocomposites　and　suppress　the　bulk　current　by　reducing　the　charge　generation　rate　and　mobilities　of　charge　carriers,　thus　resulting　in　a　decrease　in　the　volume　conductivity.　The　obtained　results　provide　a　theoretical　background　for　tailoring　PP-based　composites　for　specific　applications　by　controlling　nano-fillers.　©　2021　IOP　Publishing　Ltd.