This invention provides a novel process of using magnetically responsive fluorescent polymer particles comprising polymeric core particles coated evenly with a layer of polymer containing magnetically responsive metal oxide as highly sensitive quantitative reagents for biochemical and immunological studies, wherein the fluorescent magnetic particles can serve as a marker for the number of particles. A wide variety of polymeric particles with sizes ranging from 1 to 100 microns can be used a core particles and transformed into magnetically responsive polymer particles. The surface of these magnetically responsive polymer particles can be coated further with another layer of functionalized polymer. These magnetically responsive fluorescent polymer particles can be used for passive or covalent coupling of biological material such as antigens, antibodies, enzymes or DNA/RNA hybridization and used as solid phase for various types of immunoassays, DNA/RNA hybridization probes assays, affinity purification, cell separation and other medical, diagnostic, and industrial applications.