Benzene carboxylic acids (BCAs) are considered to be an important group of chemicals and widely used in the chemical industry. The generation of BCAs from coal via oxidation is widely studied, indicating that the distributions of BCAs are various with different coals and the yields of BCAs with lower numbers of carboxyl groups increase in the process of coalification. However, the relationship between distributions of BCAs and the aromatic clusters of coal is unclear. In this work, combined with the results of distributions of BCAs and C-13 NMR, the most probable aromatic clusters in different coals were proposed. The result indicates that, in the process of coalification (from lignite to anthracite), the aromatic cluster size and the degree of condensed aromatic rings both increase with an increase in carbon content or coal rank, but the substituted degree of aromatic rings decreases. When the carbon content of coal is lower than 87%, the aromatic rings in coal are arranged in a linear catenation manner. When the carbon content of coal is more than 87%, aromatic rings in coal are arranged in a circular catenation manner. The substituents of aromatic clusters are distributed uniformly on the aromatic rings. With the increase of coal rank, the average substituted carbon chain length (L-n) decreases; namely, more and more aromatic clusters tend to be directly connected to others. These structural features make the yields of benzene dicarboxylic acids and benzene tricarboxylic acids (BTAs) increase with coal ranks from lignite to anthracite via oxidation. The highest yield of BCAs is benzene tetracarboxylic acids from Xiaolongtan lignite to Xuanzhong bituminous coal via oxidation. With further increasing coal rank, the highest yield of BCAs is BTAs from Pingdingshan bituminous coal to Taixi anthracite via oxidation. The proposed aromatic clusters well explain the reasons that the yields of BCAs with lower numbers of carboxyl group are significantly increased with increasing coal rank.