We propose a novel approach to synthesize graphene sheets with fine quality by calcinating the composites intercalated with montmorillonite (MMT) and asphaltene. The graphene sample thus fabricated could reach 10.79 μm long, with smooth and continuous morphology and with little defects. By analyzing the XRD patterns of graphene/MMT composites at different conditions, the graphene formation mechanism is elucidated and the optimal calcination conditions are researched. This study may provide useful insights for low-cost and scalable fabrication of graphene from asphaltene extracted from heavy crude oil. © 2019 Xiaolong Wu et al.