Y/ASA composite was successfully prepared by wrapping NaY zeolite with small-crystal size in amorphous silica-alumina (ASA) gel. Characterization results show that bonding action between zeolite Y and ASA contributes new acid sites in HY/ASA, which are responsible for its higher activity in the catalytic cracking of n-decane and light diesel, comparing with the mixture-derived catalysts. HY/ASA catalyst possesses larger surface area and mesoporous volume and uniform slit-shaped mesopores, which are beneficial to the diffusion of the products and responsible for higher yield of the middle distillates. The smaller zeolite Y crystallites in Y/ASA lead to more contact points between Y crystallites and ASA and thus provide more new acid sites for the HY/ASA catalyst. The high conversion of n-decane and yield of middle distillates over the HY/ASA catalyst can be ascribed to its acid quantity and super pore structure. (c) 2012 Elsevier Inc. All rights reserved.