Carboxylic magnetic beads are superparamagnetic magnetic particles modified with carboxyl functional groups on the surface. They are a type of functional biological magnetic beads that can quickly accumulate in a magnetic field, and after leaving the magnetic field, they can contribute to the uniform dispersion of magnetic separation. Mainly used for the preparation of immunomagnetic beads. The carboxyl magnetic microspheres are monodisperse and non-agglomerated in a regular spherical shape. They have the characteristics of superparamagnetism, fast magnetic response, rich carboxyl functional groups, monodispersity and sub-micron particle size. They can be used in special chemical reagents (such as EDC). Covalently couple peptides, proteins, antibodies, oligonucleotides and other biological ligands to the surface of the microspheres under action, which is an important carrier tool in medical and molecular biology research.