Abstract: Isotropically consolidated undrained triaxial compression shear tests are performed on both undisturbed and remolded Fuzhou clays to compare their difference in mechanical behavior caused by soil structure. It is understood that the strength behavior of natural clays can be classified into three regimes: (a) the pre-yield regime, in which the undrained shear strength is controlled mainly by soil structure; (b) the transitional regime, in which the strength behavior is affected by both soil structure and stress level, and it gradually coincides with that of the remolded specimens as the soil structure gradually damages with the increase in applied stress; (c) the destructured regime, in which the strength behavior becomes the same as that of the remolded specimens.