Abstract: The southern margin of South China Sea (SCS) has abundant hydrocarbon resources. Based on high-resolution 2D seismic data, the authors conducted the research on various focused fluid flow systems and their seismic response, implications for hydrocarbon accumulations with the purpose of understanding the characteristics and their relations with hydrocarbon. Diverse focused fluid flow systems were identified, such as mud-diapir/mud-volcano, gas chimney, pipes and the focused flow fluid related fault. Different seismic characteristics are shown for these focused fluid flow systems, which include gas-bearing high-amplitude anomalous field, low-amplitude chaotic reflection, and "drop-down"/"arch up" reflections considered to be recognition marks of focused fluid flow systems that appear frequently. Focused fluid flow systems were affected by tectonic movement and sedimentation factors and were closely related to the deep high temperature and high pressure plastic fluid. Focused fluid flow systems were preferentially developed in the weak part of the strata. Focused fluid flow systems and associated faults and fractures were often used as transport channels for hydrocarbon accumulation zones. Moreover, the strong dissolved fluid and deep hydrothermal fluid transported by the fluid movement system were beneficial to the formation of reservoirs, especially the carbonate reservoirs. Focused fluid flow systems not only served as migration passage of hydrocarbons but also could improve reservoirs. Therefore, they are of great significance for hydrocarbon accumulation.