Magnetic nanoparticles are widely used for bio-medical applications such as MRI contrast agents, drug-delivery systems, cell separation and hyperthermia, thanks to their unique magnetic properties and physico-chemical characteristics. In the early stage, efforts were focused on synthesis of uniform nanoparticles of desired dimension to achieve targeted, stable functionalities. Recently, it has been of great interest in dispersion of such nanoparitcles in aqueous solution and to render the nanoparticles bio-compatible with biofunctionality on request for utilization in bio-medical fields. In this paper, we survey the research status and give prospective on future work of magnetic nanoparticles for biomedical applications.