The article presents the numerical study on the Bragg resonances of the cnoidal wave with rigid ripples on a mean flat bottom. With the application of a general laminar flow model for nonlinear wave problems (Lee and Tang, 2009), we are able to study the possible strong reflection of the cnoidal wave from rigid ripples with certain tuned spacing around the condition of Bragg resonances. In this study, we consider the weakly-nonlinear, weakly-dispersive, cnoidal waves under the viscous action of the periodic finite-amplitude ripples. The competing orders of magnitude among effects of wave nonlinearity and dispersion on the slowly evolving free surface, viscosity on the induced vortical flow near the uneven bottom, and the tuned ripple spacing on reflected wave-seabed resonances all together makes complicated interaction between the free surface and the ripple bottom. We also employ the phase plot in nonlinear dynamic theory to describe the qualitative nature of wave interaction. The detailed interferential pattern obtained from the intersected crest-lines of the incident and reflected waves is illustrated clearly during Bragg resonances.