Multi-shape memory effect (multi-SME) in amorphous polymers has attracted great attention due to their complex thermal transitions and multi-step recovery behavior. Many experimental studies have been reported for synthesis, characterization, testing and demonstration of the multi-SME. However, theoretical approaches have seldom been applied although they are critically needed to understand the principles and predict the behavior of the multi-SME in various amorphous polymers. In this study, a new thermomechanical model was proposed to describe the thermo-/chemo-responsive multi-SME of amorphous polymers with tunable segment compositions. Based on the Weibull statistical model, a new constitutive framework was established to describe temperature-, stretch ratio- and strain-dependent behaviors of thermo-/chemo-responsive multi-SME. Finally, this newly proposed model was applied to quantitatively identify the crucial factors for the thermo-/chemo-responsive shape recovery behaviors, which have been verified by the reported experimental data.