Abstract: Due to the existence of soil structure, the mechanical behavior of natural soft clay is very complicated, including time-dependency of stress-strain relation, inherent and induced anisotropy, destructuration of inter-particle bonds and soil structure with big void. Based on some phenomena, one-dimensional and three-dimensional elastic viscoplastic models were developed during the past years. In order to overcome limitations of the existing models, a series of elastic viscoplastic models are developed for natural soft clay: (1) 1D EVP model based on 1D compression tests on insensitive clays, (2) 3D EVP model based on triaxial tests on insensitive clays, (3) 1D EVP model based on 1D compression tests on structured clays, (4) 3D EVP model based on triaxial tests on structured clays and previous models. All models are validated by simulating tests under one-dimensional or/and triaxial conditions. The final version of 3D EVP model has the same experimental cost as the modified Cam clay model. Furthermore, the determination of model parameters is straightforward.