Nanometer-sized (below 100degreesnm) bimodal mesoporous aluminosilicate molecular sieves (NBMAS) are obtained by using sol-gel method and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Ordering-packed framework mesopore is created within the colloidal particles by the templating function of surfactant CTAB and disordered textual pore is formed by the aggregation of colloidal particles as an inter-particle pore. As a result of the special properties of the present material, the hydrothermal stability and catalytic life of the material is highly improved in the catalytic cracking reactions. ZSM-5, normal AIMCM-41 and amorphous alumina-silica with nanometer particle size were used in the catalytic cracking process for comparing purpose. (C) 2004 Elsevier B.V. All rights reserved.