Iron-based magnetic nanoparticle is a kind of novel nanomaterial, which has been widely used in the collection or separation of bioactive matters, targeted drug delivery, and disease diagnoses or therapy. Because of iron-based magnetic nanoparticles’ submicron dimensions, special chemical and physical properties, they are applied in the magnetic-biosensor, DNA biosensor, protein biosensor, enzyme biosensor with improved detection sensitivity, increased throughout and reduced reaction time. The iron-based magnetic nanoparticles will play important roles in the biosensor field in coming days.