Abstract: Small mountainous river systems (SMRS) play a key role in the global environmental changes and material cycle on the continental margin, and are subject to increasing human perturbation. Compared to large river systems, the SMRS are characterized by rapid and huge discharges, fast sediment transfer, and being easily influenced by extreme events and human activities, which make them more sensitive to global environmental changes. However, they have received less research attention relative to large rivers. Currently, the role of SMRS that play in the interactions among earth's spheres deserves more in-depth researches, as the concept of earth system science is put under consideration. In particular, the combination of real time and long term hydrographic observations in the fields with multi-disciplinary analytical approaches is urgently needed for better understanding the role of these rivers played on earth surface processes. The major research directions include the discharges and compositions of dissolved and particulate materials by the SMRS from continents and islands into the global oceans, under the impacts of natural environmental changes and human activities, and the difference in sediment source-to-sink processes between the SMRS and large rivers. The comprehensive understanding of SMRS will definitely increase our recognition on earth surface processes and global sea-land interactions.