A method for preparing a zeolite molecular sieve includes the steps of: (1) mixing at least one of a silicon source, an aluminum source and a phosphorus source with an alkaline substance, a template agent and water uniformly to obtain a zeolite molecular sieve precursor solution; aging the zeolite molecular sieve precursor solution at 20-30° C. for 10-15 h; and subjecting the aged solution to ionizing radiation, and then washing the obtained solid to neutrality and drying to obtain the zeolite molecular sieve. The method of the present invention is green, simple and extremely cost-effective. Under the irradiation of an ionizing radiation source, the synthesis period of zeolite molecular sieve is short and no heating is needed in the preparation process, so energy consumption is reduced and a high-pressure system is avoided.