The Multifunctional Nanomagnetic Drug Carrier is designed to achieve sustained-release, magnetic guidance, Nuclear Magnetic Resonance contrast, and targeting. This drug carrier is iron oxide nanoparticles designed to coat chemotherapeutic drugs. It coats both hydrophobic/ hydrophilic chemotherapeutic drugs and prevents instant release of drugs after injection, which may cause side effects. On the other hand, the size difference of cavities between tumor cells and normal cells leads to different permeability. Therefore, we can control drug delivery to tumor cells through controlling nanoparticle size. With target molecule attached, our carrier enhances the reaction between nanoparticles and tumor, as well as therapeutic efficacy. More importantly, through controlling external magnetic field, the drug carrier can be target to tumor areas, and the release of drug can also be controlled. Recovery after treatments is usually physicians’ major concern, and our drug carrier enhances Nuclear Magnetic Resonance contrast, which allows physicians to observe changes of tumor cells clearly after treatment and enables them to plan the next treatment.