Abstract: The ocean bottom mixed layer (BML) is a water layer near the seabed influenced by intense turbulent mixing, serving as a critical interface where physical, chemical, and biological processes converge. It plays a key role in global ocean energy and material exchange, as well as biogeochemical cycles. This paper systematically reviews the research progress on the BML, focusing on its structural characteristics, influencing mechanisms, methods for determining and parameterizing its thickness, and the global distribution patterns of BML thickness. Furthermore, future research directions are outlined. The vertical structures of temperature, salinity, and density within the BML are analyzed in detail. The influencing mechanisms are explored, including turbulent mixing induced by bottom shear flows disrupting density stratification, strong turbulence generated by internal wave breaking, topographic effects altering flow velocity and direction while enhancing shear, tidal forces periodically modulating near-bottom currents, and geothermal heating reducing stratification stability. Various methods for determining BML thickness are introduced, such as the threshold method, curvature method, maximum angle method, and relative variance method. Parameterization relationships are discussed, indicating that BML thickness is positively correlated with water depth and turbulent diffusivity but negatively correlated with buoyancy frequency. The global distribution of BML thickness exhibits significant heterogeneity, with thicker layers near mid-ocean ridges. The median BML thickness in the Atlantic, Indian, and Pacific Oceans is 40 m, 42 m, and 64 m, respectively, with a global median of 47 m. Finally, future research directions are proposed, emphasizing the need for advanced observational technologies such as deep-sea bottom-mooring systems and autonomous underwater vehicles, enhanced theoretical studies on the interactions between bottom shear flows, internal wave breaking, and topographic effects, and the development of high-resolution numerical simulation methods for the BML.