The invention relates to the field of utilization of coal resources, and discloses a 4A molecular sieve and a preparation method thereof. The method comprises the steps of enabling white mud to react with alkali liquor to obtain silicon-rich filtrate; sequentially crystallizing and roasting an aluminum chloride solution to obtain an aluminum-rich solid product; then, enabling the silicon-rich filtrate to contact the aluminum-rich solid product under the condition of a hydro-thermal synthesis reaction, and sequentially crystallizing and filtering the product obtained after the contact, wherein the aluminum chloride solution and the white mud are respectively filtrate and filter residue which are obtained by sequentially carrying out acid process aluminum extraction and filtering on a pulverized fuel ash-containing material. The method provided by the invention can fully utilize byproducts obtained by carrying out the acid process aluminum extraction on the pulverized fuel ash under the premise of avoiding or reducing the generation of NaCl so as to obtain the high bulk density 4A molecular sieve; after the method is adopted, the production cost is obviously reduced, and the comprehensive utilization rate of the pulverized fuel ash is increased.