In this study, swelling experiments for three natural solid bitumen samples in two types of organic solvents were conducted to explore the location of the swelling between the solid organic matter and solvent in the chemical structure. The relationships between the x-ray diffraction results and chemical structure changes were also investigated during swelling. The results indicated that solid organic matter with a high proportion of aliphatic carbon could dissolve more organic solvents during the swelling reaction. Additionally, aromatic hydrocarbon compounds were more prone to dissolution in solid organic matter than saturated hydrocarbons. In the chemical solid organic matter structure, almost all of the solvent swelling occurred in the aliphatic carbon region, and the micro-crystals formed by the stacking of aromatic carbon clusters were not greatly influenced by the swelling reflection. The ratio of the γ and 002-peak heights in the x-ray diffraction spectra was affected by increases in the proportion of aliphatic carbon during the swelling process, and we proposed an equation for this change. In this study, we determined the swelling site, investigated the swelling process via x-ray diffraction, and proposed several related structural parameter calculation methods to aid future research on the structure of macromolecular organic geological matter.