Large-scale sandstone intrusions are important components of many deep-water clastic systems. They were formed by the unconsolidated sandstones of early burial stages remobilizing and injecting into the overlying strata and were commonly found in fine-grained argillaceous sediments developed in polygonal fault network. They can affect the distribution of sandstone reservoir, the vertical migration and oil/gas accumulation for their high porosity and high permeability. By integrating the research results at home and abroad,the seismic character and formation mechanism of large-scale sandstone intrusions are discussed. Results shows that they often form complex and spectacular features on 3D seismic data, such as a distinctive suite of discordant, high-amplitude reflections, the opposite polarity of upper and lower reflections, conical amplitude, horizon pull-down and so on. The sandstone intrusions are resulted from extremely high pressure in deep water environment. The presence of a widespread region of conical sandstone instrusions in the deep-water basin has important implications for vertical fluid migration in the region.