According to the optical and magneto-optical characteristics of magnetic fluid, five kinds of common fiber magnetic field sensors are introduced, including fiber magnetic field sensor based on interference mechanism, fiber magnetic field sensor based on fiber grating structure, fiber magnetic field sensor based on evanescent wave mechanism, fiber magnetic field sensor based on surface plasmon resonance mechanism field sensor and fiber magnetic field sensor based on photonic band gap effect mechanism, various technical performances of magnetic fluid fiber magnetic field sensor are analyzed, and the technical difficulties are pointed out. Finally, the research direction of magnetic fluid fiber magnetic field sensor is prospected.