Commercial beta molecular sieve as part of the silicon aluminum source, TEOS as silicon source and P123 as the template agent is the preparation of composite molecular sieves beta/SBA - 15 by adopting after synthesis under hydrothermal conditions. Investigating synthesis conditions,including acid concentration, acid volume, crystallization temperature and time and so on have the impact on the synthetic samples, and their structures were characterized by adopting XRD, FT-IR and N2 adsorption - desorption methods, the results show that the acid concentration is 6 mol/L, 40 ml acid volume, beta load 50%, the crystallization temperature of 110 ℃ and 48 h crystallization time is the best synthesis condition, beta secondary structural unit into the SBA - 15 hole in the wall, hole wall become thickening. Then comparing the catalytic effect of phenol alkylating of beta, mechanical mixing and synthetic samples clearly indicates that the sample is better than that of mechanical mixing molecular sieve.