Mono-sized polystyrene microspheres are prepared from emulsion polymerization, with a variety of sizes ranging from 0.05 to 20 μm. We offer white polystyrene microspheres without surface functional groups or with carboxylated functional groups. Plain polystyrene microspheres without functional groups on the surface are suitable for binding antigens and antibodies by physical adsorption. Polystyrene microspheres with carboxylated surface functional groups can be covalently bound to antigens/haptens, antibodies, polypeptides and nucleic acid probes, providing ideal materials for immunodiagnosis and biological separation. In addition, we can provide service to develop polystyrene microspheres of customized particle sizes and surface functional groups to meet diverse needs.