Abstract: In actual production, coking coals with similar traditional coal properties, such as the bond index and plastic layer index, often produce coke with significant quality differences. To investigate the impact of coal chemical structure differences on coke quality, three coking coals with similar coal quality indices (C1, C2, C3) were selected and analyzed by preparing coke in a 40 kg coke oven. Through petrographic analysis, Gieseler fluidity measurement, fixed-bed pyrolysis experiments, and thermogravimetric analysis, combined with ¹³C NMR and Raman spectroscopy, the study examined the coking process from the perspective of coal structure transformation and correlated it with coke quality. The study found that traditional coal quality indices such as the G value and the Y value overlook the chemical structure of coal and its essential impact on coal properties and coke quality, making them insufficient to fully explain the differences in coke quality. The development of fluidity in the thermoplastic temperature region is closely related to the release behavior of volatiles. The narrow plasticity range and low fluidity of C3 lead to a decline in coke quality. Large aromatic clusters (e.g., f_ar, C_a) and short-chain hydrocarbons (low CH₂/CH₃ ratio) in C3 hinder the depolymerization of coal, affecting the development of fluidity. Additionally, the increased defect structures (f_ar^N) in coal enhance the reactivity of coke, contributing to the reduction in coke strength. The study helps evaluate and predict the coke strength of different coal types and provides new insights into optimizing coal selection and blending strategies.