Abstract: In this paper a kind of new physical models is proposed on the basis of the Iwan models. In the stress-strain relationships derived from the new physical models the backbone curve may appear in the form of work-harden or work-soften and two branches of backbone and hysteresis curves are not necessarily the same. The masing type's relationships can be obtained from the formulations of the new models. According to the new physical models, an analytical model to describe the shear stress-shear strain relationships of soils under cyclic loadings is suggested and the hyperbolic model is only a particular case of such model. Finally, the steady-state response of the nonlinear system depicted by new physical models under harmonic force is discussed.