Biomass-based energy fulfills the future need of sustainable humanity. The utilization of lignin which is a primary constituent of biomass still remains the world most difficult problem due to its highly aromatic polymeric structure. Investigations on lignin model compounds renew the knowledge on CC and CO bond cleavage chemistry and indicate directions for lignin deconstruction. This review is to present the state of the art of the chemical transformation of lignin model compounds including monomers and dimers based on catalyst classifications, with emphasis on the fundamental catalytic chemistry in different processes. Moreover, how ideas derived from concepts transform to strategies for controlling the reaction pathways is also discussed.