Abstract: Based on non-stationary viscous components, the non-stationary Maxwell model, the non-stationary Kelvin model and the non-stationary Zener model were developed. Their relaxation moduli, creep compliances and unloading functions were obtained by resolving the non-stationary constitutive relation. The results show that many empirical functions, such as power law relaxation, stretched exponential relaxation, logarithmic creep, can be seen as non-stationary model. The corresponding relaxation modulus and unloading functions of empirical creep functions, the corresponding creep compliance and unloading functions of empirical relaxation function were obtained by resolving the non-stationary constitutive relation.