To evaluate the characteristics of soft soil in the Yushan Island sea area，we research the physical and mechanical property indices and spatial distribution development characteristics of soft clay layer based on the analysis of a large number of investigation data from the drilling，vane shear test and geotechnical test data in the sea area near Yushan Island，and conclude that soft soils in the Yushan Island sea area are mainly silty，powdery clay layers interspersed with thin layers of more chalky sand，and its thickness and depth of burial gradually increase from the pre-hill alluvial zone to the coastal zone. Meanwhile，we propose the soft ground treatment method in the Yushan area.