Nano-crystallite oriented self-assembled ZSM-5 zeolite (NS-Z5) is successfully synthesized with high yield of 85% by a facile salt-aided seed-induced method within 1.5 h at TPABr (tetrapropylammonium bromide)/SiO2 ratio of 0.1. The systematic and thorough characterizations, involving morphology, textural/structure property, and acidity, indicate that NS-Z5 particle is composed of oriented-assembled high-crystalline zeolite MFI nano-crystallites and possesses abundant accessible strong acid sites due to its large/rough external surface. The strong acidity of NS-Z5 sample results from its high crystallinity and few framework defects benefiting from the introduction of seeds. The catalytic evaluations both in batch and in thermogravimetric reactors demonstrate the important roles of the accessibility and strength of acid sites on low-density polypropylene cracking. This paper provides a facile method for preparation of hierarchical high-crystalline ZSM-5 nano-zeolite and confirms the significance to synchronously maintain large amount and high strength of accessible acid sites on large molecule conversion. (C) 2013 Elsevier Inc. All rights reserved.