In the process of foundation pit excavation, the soil mass in different parts shows dynamic destruction characteristics due to diverse unloading mechanics. In order to study the complex unloading stress path in the foundation excavation, the TSZ-1S stress control triaxial compression apparatus is used to carry out the loading and unloading tests of the lacustrine sedimentary peat soil under the conditions of consolidation undrained and K0
consolidation, respectively, and the test scheme is formulated according to different unloading conditions such as lateral, axial and axial lateral meantime unloading, so as to simulate the stress-strain curves of soil under different unloading paths in the foundation excavation and the variation laws of strength and initial tangent modulus under unloading shear failure. The test results show that the stress-strain characteristics of soil are closely related to the stress path, and the stress-strain curves under each path are approximately hyperbolic. The strength of unloading shear failure is significantly lower than that of loading failure. The study of initial tangent modulus Ei
under different unloading paths shows that Ei
is greatly affected by lateral unloading, Ei
increases after unloading, and axial unloading has little effect on it. The stress-strain curves are normalized, and the normalization equation of peat soil considering different normalization factors is constructed. Based on this equation, the peat soil under different stress paths is normalized, and the results are verified. The results of this work can provide reference for the study of deformation parameters and constitutive relations of foundation pits on peat soil sites under different unloading paths.