The invention relates to the field of coal resource utilization and discloses a 4A type molecular sieve and a preparation method thereof. The method comprises the following steps: (1) performing reaction on coal ash under the acidic condition to obtain a mixture; (2) filtering the mixture to obtain filter residue and AlCl3 mother liquid separately; (3) performing reaction on the filter residue under the alkaline condition to obtain Na2SiO3 mother liquid; and (4) performing mixing reaction and crystallization on the AlCl3 mother liquid and the Na2SiO3 mother liquid sequentially. By the method provided by the invention, the 4A type molecular sieve with high purity and crystallization degree can be prepared by treating the coal ash with high price and huge yield by an acid dissolution method.