Nanocrystalline ZSM⁃5 zeolites were synthesized by hydrothermal synthesis using 30% silica sol as silica source and aluminium sulfate as aluminium source. The obtained samples were characterized by XRD, SEM, BET and NH3⁃TPD characterization methods, and the effects of different pH on the physico⁃chemical properties of nanocrystalline accumulation ZSM⁃5 molecular sieve were investigated. The results showed that when the pH value was 11.50, the catalyst had nano⁃scale structure, large surface area, large number of mesopores and suitable acidity. The application of thiophene alkylation showed better thiophene alkylation activity.