Abstract: Graphene has shown promising prospects in the fields of electronics, new energy, and new materials due to its excellent physicochemical properties. The preparation of graphene from bituminous coal not only expands the range of graphene raw materials but also reduces carbon emissions from coal chemical processes. In this study, graphene was prepared from ShenDong bituminous coal using an improved Hummer's method. The crystal structure, morphology, and thickness of the graphene and its intermediates during the preparation process were characterized qualitatively and quantitatively using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The influence of the particle size of the coal powder raw material on the structure of the prepared graphene was also investigated. The results showed that bituminous coal of different particle sizes could form highly ordered graphite crystal structures through high-temperature graphitization, and thus be successfully converted into graphene. The XRD patterns exhibited distinct graphene characteristic diffraction peaks, and the Raman spectra showed typical graphene defects and sp² hybridization plane features. As the particle size of bituminous coal increased, the defects in the prepared graphene increased. The graphene samples obtained from coal with a particle size of 46.89 μm had small graphene microcrystalline stacking thickness and high defect levels. SEM, TEM, and AFM characterizations revealed that the prepared coal-based graphene nanosheets had wrinkled surfaces and were 1−2 layers thick, meeting the standard of few-layer graphene. This study provided new ideas for the high-value utilization of bituminous coal, and helped to promote the transformation of fuel coal to material coal and the realization of the dual-carbon goals.