Influence of the ionic compositions of bathing solution with multivalences is investigated on the responsive behavior of pH-sensitive hydrogel to environmental change in solution pH. It is based on a chemo-electromechanical formulation, previously termed the multieffect-coupling pH-stimulus (MECpH) model, which is improved in this article by incorporating the finite deformation theory into the mechanical equilibrium. The improved MECpH model consists of the coupled non-linear partial differential equations, which are solved via a meshless numerical technique called the Hermite-cloud method with the modified Newton iteration. After the MECpH model is examined by comparison between the computational results and experimental data available in literature, several case studies are numerically carried out to discuss the effects of the multivalent ionic compositions of surrounding solution on the variation of the deformation of the pH-stimulus-responsive hydrogel and the distributions of the diffusive ion concentrations and electric potential, when the hydrogel is placed in the buffered solutions. POLYM. ENG. SCI., 50:429-439, 2010. (C) 2009 Society of Plastics Engineers