High-silica-content mordenite with different SiO 2 /Al 2 O 3 ratios (10.8-32.2) was prepared by the addition of benzene-1,2-diol into the system, 10SiO 2 :Al 2 O 3 :3Na 2 O:500H 2 O:(0-5.0)C 6 H 6 O 2 (C 6 H 6 O 2 : benzene-1,2-diol). Experimental results showed that the content of benzene-1,2-diol in the reaction mixture largely influenced the ratios of silicon to aluminium of mordenite crystals and the crystallinity rate. The role of benzene-1,2-diol in the reaction mixture was investigated by 2 7 Al NMR and 2 9 Si NMR, and it was shown that an aluminium-benzene-1,2-diol complex was possibly formed in the reaction system, which may be responsible for the formation of high-silica-content mordenite.