It is hard to achieve a satisfactory flotation performance of ultrafine pyrite in alkaline solution using the conventional xanthate collectors. In this work, a novel nanoparticle flotation collector Zijin Nanomaterial (ZJNM) was prepared by emulsion polymerization to enhance the flotation of ultrafine pyrite. It was found that ZJNM was effective in the flotation of ultrafine pyrite with diameter smaller than 18 μm in alkaline solution, which was independent on pH. Mechanism study indicated that the surface of pyrite in alkaline solution was composed of unoxidized surface area and oxidized surface area. ZJNM could adsorb on the unoxidized pyrite surface by forming Fe-S between S atoms on nanoparticles and Fe atoms on pyrite surface, and adsorb on oxidized pyrite surface through hydrogen bonding between -NH₂ on nanoparticles and Fe-OH on pyrite surface, thus increasing the overall hydrophobicity of pyrite and benefit flotation. This work is of guiding significance to enhance the flotation of ultrafine pyrite in practice.