Well-dispersed hierarchical zeolite Y, structure-directed by ionic liquid 1-methyl-3-[3'-(trimethoxysilyl) propyl] imidazolium chloride, was synthesized for the first time using a novel ultrasonic/microwave synergistic synthesis (UMSS). The time required for the synthesis of zeolite Y by UMSS method was remarkably reduced to 6 h instead of 24 h under conventional hydrothermal conditions. The structures of all samples were characterized by XRD, BET, FT-IR, SEM and TEM. The results clearly demonstrated that the UMSS is a promising strategy to achieve zeolite Y with improved crystallinity, large BET surface area, bulky mesopore volume, well-dispersed morphology, small zeolite nanoparticle. The catalytic activity of hierarchically micro-mesoporous zeolite Y was evaluated by using the alkylation of o-xylene with styrene. Mesoporous zeolite Y synthesized by UMSS method showed significantly higher catalytic activity, stability and reusability, compared with conventional hydrothermal synthesis. It might be ascribed to its large mesoporous volume, small crystal nanoparticle and high surface area, minimizing the diffusion length as the reactant molecules diffuse into the pores, and correspondingly the products diffuse out of zeolites. This study suggests that UMSS method is a good alternative for the synthesis of micro-mesoporous zeolite Y, which may be of remarkable benefit for industrial applications.