Melanin nanoparticles (MNPs) not only retain the inherent characteristics of melanin (metal ion chelation, photothermal conversion property, etc.), but also can exhibit more excellent properties, such as high dispersion stability, good biocompatibility and biodegradability, etc. Furthermore, these performances can be enhanced to target the specific sites and treat diseases by the surface modification or combination with functional substance. In this paper, the characteristics, preparation methods and applications of MNPs were reviewed. It provides a reference for further development of application for MNPs, and theoretical basis for practice in biology, medicine and so on.