Ground　calcium　carbonate　(GCC)　has　the　effect　of　reducing　the　incremental　cost　and　improving　the　application　performance　as　a　plastic　filler.　In　this　study,　waterborne　polyurethane　(WPU)　was　employed　as　a　novel　modifier　for　the　wet　modification　of　GCC.　Polypropylene　(PP)-based　composites　incorporating　GCC　were　then　prepared　for　mechanical　properties　testing.　The　oil　absorption　value,　wetting　contact　angle,　and　settling　time　in　kerosene　indicated　that　the　modified　GCC　achieved　an　excellent　modification　effect　with　a　WPU　dosage　of　2.0　wt%.　The　X-ray　Diffraction,　Fourier　Transform　Infrared　Spectroscopy,　and　X-ray　Photoelectron　Spectroscopy　results　indicate　that　WPU　was　successfully　coated　on　the　surface　of　the　GCC.　SEM　images　revealed　improved　wettability　and　compatibility　of　GCC　in　the　composites　after　modification.　The　mechanical　tests　showed　that　the　GCC-WPU/PP　composites　exhibited　enhanced　properties,　including　a　flexural　strength　of　107　MPa,　impact　strength　of　9.54　kJ/m2,　tensile　strength　of　29.7　MPa,　and　an　elongation　at　break　of　30.9%.　Highlights:　WPU　was　innovatively　used　as　a　modifier　of　GCC.　An　optimal　modification　effect　was　gained　at　the　low　dosage　(2.0　wt%).　GCC　has　excellent　compatibility　and　wettability　in　PP　composites.　The　obtained　PP-based　composites　have　better　mechanical　properties.　The　study　has　the　potential　to　apply　GCC　in　plastics　and　other　industries.　©　2024　Society　of　Plastics　Engineers.