In this paper, a chemo-electro-mechanical model is presented which considers the characteristics of the three phases of the ionic-strength-sensitive hydrogel, including the solid polymeric network matrix, interstitial fluid and ionic species. It is termed the multi-effect-coupling ionic-strength-stimulus (MECis) model and composed of Poisson-Nernst-Planck system for diffusion of the chemical ionic species in the interior hydrogel and external solution, associated with the fixed charge equation for simulating the interaction between the fixed charges and mobile ions, and the mechanical equilibrium equation to characterize the deformation behavior of the solid polymeric network matrix. The simulation results of the MECis model are examined by comparing with the experimental data published in open literature. It is demonstrated that the present MECis model could simulate well the responsive behavior of the ionicstrength-sensitive hydrogel quantitatively. The parameter study is conducted by the MECis model for analysis of the influence of the Young's modulus on the characteristics of the smart hydrogel, and it is concluded that the present model can be employed as a good platform for design and optimization of the smart hydrogel-based BioMEMS.