Abstract: The research indicates that with the increase of the organic matter content,some indexes such as natural water content and natural void ratio increase in linear regularity,and some other indexes such as vane shear strength,specific penetration resistance,permeability coefficient,and consolidation coefficient decrease.When organic matter content reaches to 1.74%,the physical and mechanical characters of soft soils have a big change,that means the soften effects on mechanical properties are especially distinct;meanwhile,the permeability capacity reaches to the maximum value.