Nano-sized Beta zeolites, with a crystal size of 80-100 nm, were synthesized via surface wet method. The nano-sized HBeta zeolites exhibit much higher activity and stability in the Friedel-Crafts acylation of anisole and toluene with acetic anhydride than the conventional zeolites of large particle size. The small crystal size of nano-sized zeolites may bring on more accessible active sites and then enhance the catalytic activity. The exposed pore openings in nano-sized zeolites allow a fast desorption of heavy products from the catalyst and can then reduce the occupancy of active sites by the adsorption of products; this can then alleviate the catalyst deactivation and improve the catalyst stability.