Based on engineering examples offshore in the Yushan area and geotechnical engineering investigation results，in view of the variability of the vertical and horizontal engineering geological characteristics of the thick soft soil layer widely developed in the shallow part of the Yushan offshore，we carry out segmented analysis and comparison by the method of mathematical statistics，probe into the variability of the physical and mechanical properties under different buried depths and reveals its variation law with the buried depth，to provide technical reference for identification of the engineering geological characteristics of thick soft soil and determination of the scope and depth of foundation treatment，and foundation reinforcement technology. The analysis results show that with the change of the buried depth，the engineering geological property of thick soft soils changes，and the engineering geological property at the bottom are better than that at the top.