The　direct　and　rapid　determination　of　trace　cobalt　ion　(Co2+)　in　the　electrolyte　of　zinc　smelting　plants　is　urgently　needed　but　is　impeded　by　the　severe　interference　of　extremely　high-concentration　zinc　ions　in　the　solution.　Herein,　colorimetric　detection　of　Co2+　by　the　polyvinylpyrrolidone　functionalized　silver　nanoparticles　(PVP-AgNPs)　is　realized　in　solutions　with　the　Zn/Co　ratio　being　high,　up　to　(0.8–5)　×　104,　which　is　located　within　the　ratio　range　in　industrial　solution.　The　high　concentration　of　Zn2+　induces　a　strong　attenuation　of　Co2+-related　signals　in　ultraviolet-visible　(UV-vis)　extinction　spectra;　nevertheless,　a　good　linear　range　for　detecting　1–6　mg/L　Co2+　in　50　g/L　Zn2+　solution　is　still　acquired.　The　strong　anti-interference　toward　other　metal　ions　and　the　mechanism　understanding　for　trace　Co2+　detection　in　such　a　high-concentration　Zn2+　solution　are　also　revealed　by　systematic　analysis　techniques.　The　results　extend　the　AgNPs　as　colorimetric　sensors　to　industrial　solutions,　providing　a　new　strategy　for　detecting　trace-metal　ions　in　industrial　plants.　©　2023　by　the　authors.