The existing one-dimensional constitutive model for shape memory alloys is extended to take account of the porosity and the strain rate effect by using the internal state variables representing the porosity and the martensite volume fraction. The proposed constitutive equation is applied to the simulations for the quasi-static and the dynamic behaviors of dense and porous shape memory alloys at various temperatures and strain rates. The calculated results are compared with the uniaxial test results for dense and porous NiTi alloys to illustrate the validity of the present constitutive modeling. It is expected that the finite element program implementing the proposed constitutive equation will be a powerful tool to predict the mechanical behaviors of various porous shape memory alloy devices.