An effective way (without addition of any oxidative gases to the reactant) to suppress coke formation (by modification of the Mo/HZSM-5 catalyst) and thus to significantly improve the aromatic selectivity in the methane aromatization reaction is presented in this study. A greater yield of benzene and an enhanced durability of the catalyst when compared with the conventional Mo/HZSM-5 catalysts are observed. Multinuclear solid-state NMR, TPD, TPO, TG, and UV-Raman methods are applied to characterize and rationalize the structure-property relationship of the improved catalytic performance of the modified catalysts. From this work, we found that only a small fraction of tetrahedral framework aluminum, which corresponds to the Bronsted acid sites, is sufficient to accomplish the aromatization of the intermediates in methane aromatization reaction, while the superfluous strong Bronsted acid sites, which can be removed upon steaming treatment, are shown to be related with the aromatic carbonaceous deposits on the catalysts.