Abstract: The method of calculating foundation settlement by the secant modulus method is becoming familiar to scholars for its unique advantages， but a large number of studies have found that the calculation results are small when using this method for foundation settlement calculation. This is because the traditional secant modulus method treats the relation between vertical stress and vertical strain in the lateral limit compression test as hyperbolic and ignores the reference configuration， which limits the applicability of the method and affects the calculation accuracy. The stress-strain curves of Kunming peaty soil and silt were fitted with various functions by conducting a large number of high-pressure consolidation tests. The test results showed that the stress-strain curves of Kunming peaty soil and silt in lateral limit conditions could be better characterized by Gunary’s model than the assumption of the hyperbolic model， and the foundation deformation equation considering the overburden load and burial depth change was established based on the improved the secant modulus method with the introduction of correction factor γ. It is found that the relation between secant moduli and burial depth varied greatly for different soils， among which the relation between secant moduli and burial depth of peaty soil was in accordance with ExpDec1 expression.