Abstract: Deep-sea soft soil often leads to settlement failure of marine engineering structures due to its high compressibility. China has carried out a series of engineering constructions and resource developments in the South China Sea in recent years. However,due to insufficient understanding of deep-sea soft soil,deep-sea engineering construction and resource development face severe challenges. Through whole-rock analysis,consolidation compression,and compression-rebound-recompression tests,this work studies the compression properties of deep-sea sedimentary soft soil in the South China Sea and analyzes the effects of initial void ratio,stress history,and water content on compression. The results indicate that the soft soil is clay with a high liquid plastic limit,and the mineral components are mainly calcite and illite,which have poor particle gradation. The relationship between settlement and time of saturated soil under fixed load can be described by a hyperbolic model. The compression coefficient is much larger than 0.5 MPa^-1. The compression index first increases linearly and then slowly increases when 200~400 kPa,and rapidly increases in the last. The e-lgp curve presents a slow front and steep back shape,and there is an obvious turning point(yield stress). The deformation before yielding is small and increases rapidly after yielding. The relationship between initial water content and yield stress can be described as a power function.