Deep sea circulation is important for world climate and has been a substantial research area in ocean science, leading to various breakthroughs and discoveries. With the rapid advance in research on ocean science, these matters have received increasing attention from the oceanography community. In this article, we attempt to convey the progress made in recent years. We first provide an overview of existing observations, theories, and simulations of deep South China Sea circulation. Finally, we discuss remaining issues. With the rapid advance in research on ocean science, these matters have received increased attention from the oceanography community. In this article , we attempt to convey the progress made in recent years. We first provide an overview of existing observations, theories, and simulations of deep South China Sea circulation. Finally, we discuss remaining issues.