Abstract: Through compression experiment on the soil columns from the Pearl River Delta and quantitative study of the microstructure variations of the pressed mud column, the author obtains the formulas for calculating the unit and total settlements with depths under a certain pressure. On the basis, the paper further discusses the relationship between the content of natural water in soft soil and the settlement value under a certain load, and corrects the parameter "c" of the formula for total settlement. These formulas should be helpful for the calculation of settlement value during designations of engineering