Abstract: Mass transport deposits (MTDs) are currently a hot topic in marine research, but the morphological characteristics of mass transport deposits remain unclear. Based on high-precision three-dimensional seismic data from Lingshui Sag in Qiongdongnan Basin, this article describes the three-dimensional seismic configuration of mass transport deposits in Lingshui Sag. It studies the internal structure, characteristics and formation mechanism of deep-water sediments in the basin, and identifies structural features such as erosion scratches, thrust nappe structures, compression ridges and channels. The causes and distribution of MTDs are speculated by studying their sectional and planar characteristics. Finally, the special structures formed by MTDs are discussed and three hypotheses are put forward. MTDs exist before the flow initiation and it is transported passively within layers; MTDs are formed during flow movement; MTDs are formed during the flow stagnation. The MTDs sedimentary layers are dense inside with few penetrative structures, making them excellent cap rocks for oil and gas reservoirs.