The invention provides a preparation method of an MCM-22 molecular sieve catalyst. The preparation method comprises the following specific steps of treating a template-containing Na-type MCM-22 molecular sieve for 10-180 min with a 0.1-1.0 mol/L alkaline solution at the temperature of 20-100 DEG C; washing the obtained product to a neutral state; drying and roasting the product to remove the templates; exchanging with a ammonium nitrate solution; filtering; washing with deionized water; and drying and roasting to form an H-type catalyst. Partial of the templates in the molecular sieve skeleton can be recovered to the alkaline solution during the process of preparing the catalyst by the alkaline modification of the MCM-22 molecular sieve. Compared with an MCM-22 molecular sieve catalyst unprocessed by the alkaline solution, the alkaline-modified MCM-22 molecular sieve catalyst is significantly improved in catalytic activity for the reaction of the benzene and dialkyl benzene.