In this paper, a novel plate theory is proposed for corrugated soft panels with a chemically coupled constitutive model of hydrogel, which is formulated via perturbation analysis on the physically based constitutive theory. Here, the elastic moduli naturally incorporate the chemical effects that could reduce to the classical linear Hookean law or second-order Murnaghan model. As a result, the resultant constitutive model is concise in form and comprehensive in physical integrity, where no further coupling is required between the deformation of solid and diffusion of fluid. Applying the symplectic elasticity method, the exact bending solution is then derived for corrugated hydrogel panels with two opposite sided clamped. The main effects of chemical potential, Flory parameter, and geometric factors on the equivalent stiffnesses and transverse deflections are investigated in detail. Some new results could be used as a reference for the designing of flexible and wearable devices.