Low-rank coals (LRCs) are abundant and represent potential supplementary resources for coking blends, but their poor caking ability limits their direct utilization. Hydrogen-donor solvent modification can improve the caking behavior of selected LRCs, while the changes in solvent-extractable fractions during modification and their relationship with caking behavior are not yet fully understood. In this study, two representative LRCs, Hequ coal (HQ) and Hami coal (HM), were modified under catalyst-free conditions using hydrogen-donor solvent systems. The effects of coal type, reaction temperature, initial pressure, and solvent hydrogen supply capability value (HSCV) on the modification performance were examined. HQ showed a much greater improvement in caking ability than HM. At 380 °C and an initial N₂ pressure of 4 MPa, with tetralin as the hydrogen-donor solvent, the G_RI of HQ increased from 0.1 to 84.8, and the yield of the modified coal was 78.0%. The better performance of HQ is associated with its relatively short and highly branched aliphatic structures, which favor the formation of mobile intermediates during thermal conversion. As the temperature increased from 340 to 400 °C, the G_RI first increased and then decreased, reaching a maximum at 380 °C, whereas the effect of initial pressure was relatively limited under the examined conditions. As HSCV increased from 0 to 1, the availability of active hydrogen increased, favoring the stabilization of pyrolysis-derived radicals and the suppression of excessive condensation, thereby improving the caking ability. Structural characterization showed that hydrogen-donor solvent modification was accompanied by a reduction in oxygen-containing functional groups, shortening and branching of aliphatic chains, and changes in aromatic structures, indicating that radical stabilization and structural rearrangement are closely related to changes in caking behavior. On this basis, HQ was selected for further study. Representative modified coals obtained at different temperatures and HSCVs were subjected to sequential solvent extraction to determine the yields, structural characteristics, thermal behavior, and caking properties of the resulting fractions. These data were correlated with the overall G_RI of the modified coals to examine the relationship between the evolution of solvent-extractable fractions and caking behavior. This work improves the understanding of structural and compositional changes in low-rank coal during hydrogen-donor solvent modification, provides insight into the relationship between the evolution of solvent-extractable fractions and caking behavior, and offers a basis for the upgrading and utilization of low-rank coal in coking blends.