Here we report the preparation of novel rice husk ash - reduced graphene oxide nanocomposites and their catalytic application in Biginelli reaction. Hydrothermal treatment is given to a mixture of rice husk ash and graphene oxide for the formation of a uniform composite. XRD and FTIR spectral analyses confirmed the partial reduction of graphene oxide in the nanocomposites during hydrothermal treatment. The binding between rice husk silica particles and graphene sheets through Si-O-C bonding is revealed from XPS analysis. Graphene is found to be less defective in nature in the composite as evident from the reduced I-D/I-G value in the Raman spectrum. SEM and TEM images showed the effective dispersion of rice husk SiO2 particles on the wrinkled graphene layers. Present study also exploited the use of a statistical model, response surface methodology, for the optimization of reaction parameters on the catalytic synthesis of dihydropyrimidinones via multicomponent solvent free Biginelli reaction. The cost effective highly efficient rice husk ash - reduced graphene oxide catalyst is found to be reusable till 7 repeated cycles with only about 4% reduction of its initial activity.