Abstract：In the intricate domain of marine geochemistry, barium (Ba) and its isotopes emerge as pivotal elements. Their remarkable high preservation rate within marine sediments endows them with the ability to withstand post-depositional alterations, making them ideal candidates for long-term geological records. The stable isotope fractionation property of barium isotopes serves as a powerful tool, enabling scientists to reconstruct paleoproductivity with a high degree of precision. In the course of this research, we meticulously collated high-precision isotope analysis data from various sources. This data-gathering process involved a comprehensive review of existing literature and in-house experimental results. Subsequently, we delved into an indepth exploration of the sources and sinks of marine barium. Our research findings vividly demonstrate that terrigenous, hydrothermal, and biological inputs are not isolated factors but rather collaborate in a complex symphony to drive the cycling of barium in the ocean.Regarding Ba isotope fractionation, within the mineralfluid- melt fractionation system, we uncovered that the dynamic interplay between equilibrium and kinetic fractionation mechanisms is of paramount importance. The equilibrium fractionation, which is rooted in quantum mechanical differences in bond vibrations, and the kinetic fractionation, which is associated with non-equilibrium processes such as diffusion, jointly shape the isotopic composition of barium in the marine environment. The observed regional differences in fractionation further suggest that multiple factors, including temperature, pressure, and the presence of various chemical species, jointly influence marine Ba isotope fractionation. This spatial heterogeneity provides an invaluable basis for tracing the evolution of the paleo-oceanic environment, allowing us to piece together the historical changes in oceanic conditions.Looking ahead, the integration of in-situ micro-area techniques is not merely a desirable approach but an essential one. These advanced techniques will enable us to peer into the microscopic world of marine systems, facilitating a more profound understanding of how biology, minerals, and fluids interact at the microscale. By doing so, we can enhance the accuracy of paleooceanic environment reconstructions, bringing us closer to a more comprehensive understanding of Earth’s past oceanic ecosystems.