The invention discloses a preparation method of zeolite. High-alumina fly ash or roasted and activated fly ash is taken as a raw material, after the high-alumina fly ash or the roasted and activated fly ash is magnetically separated for iron removal, the monomer dissociation degree of mineral in the fly ash is improved by adopting a mechanical activation manner, and a zeolite product is prepared from the fly ash after mechanical activation in alkaline liquor by adopting a direct hydro-thermal synthesis manner. According to the preparation method, the industrial waste, namely the high-alumina fly ash can be effectively utilized for preparing the products of a zeolite sieve and the like, and high efficiency and high-value utilization of high-alumina fly ash are realized.