The invention discloses a functionable superparamagnetic nano particle with uniform particle size. The nano particle is provided with a superparamagnetic nano particle core, and the magnetic nano particle core is connected with a plurality of water-soluble polymer chain segments and organic chain segments containing modifiable amino terminal groups respectively; and the magnetic nano-particle core is an MFe2O4 superparamagnetic nano particle, wherein metal M is one of Fe, Co and Mn, namely the magnetic nano particle is one of Fe3O4, CoFe2O4 or MnFe2O4, the particle size of the magnetic nano particle is between 4 and 12nm, and the particle size distribution is not more than 20 percent. The synthesized material can be widely applied to targeted release of medicaments, magnetic fluid hyperthermia, biofluorescent detection and the like. The synthesized magnetic nano-particle has uniform particle size, which ensures that the nano-particle meets the demand of biological application. At the same time, the surface of the nano-particle is modified with an organosilicon compound with an amino group remained at a terminal, and the amino group can be widely combined with bio-functional substances, thereby ensuring that the synthesized magnetic nano-particle can conveniently perform the bio-functionalization.