Abstract: The engineering properties of saturated cohesive soil are closely related to its stress state. In order to choose the method for shear strength tests correctly, the stress state of foundation soil under natural condition and engineering design must be considered. Through geotechnical tests on undisturbed soil, the influence of test methods on shear strength indexes is analyzed. It is proposed that disturbed soil samples derived from the field should be pretreated in the lab for shear strength tests so as to restore their initial stress state. According to the need of practical engineering problems, shear tests on soil samples should be performed to determine consolidation pressure and drainage conditions. In order to determine shear strength indexes, stress conditions of engineering application are supposed to be distinguished. Moreover, statistical analysis about the test data should be carried out respectively for the pressure section which is greater than the previous consolidation pressure and that which is smaller than the previous consolidation pressure.