Abstract: The breakthrough advances in nanogeoscience research have been facilitated by innovations in modern analytical techniques, driving earth science research towards the gradual realization of coordinated multi-sphere observations spanning from the macroscopic down to the nanoscale. However, the bottleneck in efficiently separating nanoparticles from complex geological matrices constrains the in-depth application of high-precision analytical techniques, making it challenging to meet the current nanogeoscience research demands for highly accurate and multi-dimensional characterization. Field-flow fractionation (FFF) is a separation technique based on the combined action of an externally applied force field perpendicular to the separation channel and the laminar flow within the channel, achieving separation according to differences in particle size. Theoretically, it can gently yet efficiently separate particles ranging in size from 1nm to 100μm. It not only possesses high-resolution separation capabilities but also enables online coupling with various detectors. While achieving precise sample separation, it simultaneously accomplishes real-time characterization of multi-dimensional parameters such as size distribution, chemical composition, and even morphological structure, thereby providing a powerful integrated analytical platform for deciphering complex samples. Building upon an introduction to the principles, classifications, and characteristics of FFF technology, this paper exemplifies its innovative applications in nanogeoscience through the multi-dimensional sample separation and characterization capabilities afforded by its hyphenation with instruments. These applications include high-resolution separation of complex matrices, nano-scale analysis of geochemical element fractionation mechanisms, and analysis of contaminant transport pathways in environmental geology. Concurrently, it analyzes the current limitations of the technology in the practical separation of geological samples from a methodological perspective, and briefly outlines key technological directions awaiting breakthroughs, along with related recommendations, for future in-depth research in earth science.