The failure surface in most cases intersects the reinforcement layers obliquely in most reinforced soil structures, subjecting the reinforcement to an oblique force instead of axial force by the sliding mass resulting in an additional bond resistance and a decrease in net destabilizing force significantly. The pseudo-dynamic method that considers the seismic inertia force based on the effect of phase difference in shear and primary waves propagating through the reinforced backfill is studied here instead of the approximate pseudostatic seismic earth pressure. This paper presents a more rational analysis of internal stability of reinforced soil structures considering the effect of kinematics of the sliding mass.