Magnetic fluids (MF) feature with various excellent magneto-optical properties, which provides a new way for the realization of optical fiber magnetic field sensors. After more than ten years of development, it has become an important research direction in the field of optical fiber magnetic sensing. A large number of MF based optical-fiber magnetic field sensors employing different structures and principles have been proposed so far, and in general they have experienced the development from scalar to vector magnetic field sensing. In this review, the magneto-optical properties of MF and realization methods of the MF-based magnetic sensors are sorted out and summarized. Finally, some problems that still exist at present are pointed out, and prospections are made about this field.