Semi-Interpenetrating networks (SIPN) hydrogel composed of poly (acrylic acid) (PAA) and poly (vinyl alcohol) (PVA) was prepared by free radical solution polymerization. The SIPN was characterized by Fourier transform infrared spectroscopy (FTIR). The electric stimuli responsive characteristics were investigated. The hydrogel bent toward the anode initially, altered the bending direction for two times and bent toward the anode ultimately when it was placed in a 0.1 M NaCl aqueous solution under non-contact DC field. For interpreting the special deformation the osmotic pressure curves according to Shiga’ osmotic pressure model were simulated and the pH gradient theory was applied to explain the final direction.