Abstract: A large deflection bending model is developed for incompressible fluid saturated orthotropic poroelastic plates, and the corresponding basic governing equations are presented. In this model, the Kirchhoff hypotheses and the linear constitutive law are employed. The Darcy’s law is used to describe the fluid flow in pores, which diffusion is in the plate-plane directions only. According to the model, the nonlinear dynamic and quasi-static bending responses of a simply-supported rectangular orthotropic poroelastic plate with permeable conditions, subjected to a step load, are studied with Galerkin truncation method. The numerical results reveal the global drain and suction processes of fluid along the thickness direction of the plate. When the loading increases and the plate deflection thusly produced is larger, the difference between the results obtained respectively by the small and larger deflection bending models is obvious, and for quasi-static bending problem, the Mandel-Cryer effect exists in the evolutions of the plate deflection and pore pressure moment resultant on the larger deflection bending model whereas this effect never appears on the small deflection bending model.