Hierarchical ZSM-11 zeolites (Z-xat) were prepared by treating the pristine ZSM-11 zeolite in a solution of NaOH with different concentrations (C (NaOH)). It was found the porosity and acidity (concentration, strength, distribution and accessibility factor of Bronsted and Lewis acid sites) of modified ZSM-11 zeolite changed obviously with C (NaOH). When used for alkylation of benzene with dimethyl ether, the modified Z-xat exhibited better reaction stability than the unmodified HZSM-11 zeolite. Typically, the reaction stability of Z-xat zeolite catalysts was directly related to the mesopore volume, besides the weak-medium acid concentrations determined by Py-IR technique. [GRAPHICS] .