We report the investigations on structural modifications in monolayer graphene induced by low-power-density CO2 laser irradiation (2-60 W/cm(2)). Observed modifications in graphene include the disassembly of crystalline graphene into nanocrystalline structure and the generation of amorphous carbon. It was found that thermal effect played an important role during laser irradiation. By adjusting laser power density, irradiation time and temperature, the structure of graphene can be modified accordingly in a controlled manner. Our approach may enable high-efficiency and economical modification of large-area graphene, which relies on large-area irradiation using low-power-density laser. (C) 2013 Elsevier B.V. All rights reserved.