Facing people's increasing demand for optical fiber sensing, the capacity advantage of multimode optical fiber provides new ideas for solving the capacity barrier of single mode fiber and realizing high-precision multi-parameter optical fiber sensing measurement. This paper analyzes the mode characteristics of multimode fiber theoretically, reviews the research progress of multimode fiber mode coupling and polarization, and focuses on the dynamic development of the threshold, gain spectrum and Brillouin frequency shift of Brillouin scattering in multimode fiber, and analyzes the future development direction of optical fiber sensing.