The invention discloses a method for preparing 4A 
zeolite from 
gangue serving as a 
raw material through two-step 
hydrothermal synthesis. The method comprises the following steps: firstly, crushing andgrinding 
gangue, performing thermal activation pretreatment, mixing the 
gangue subjected to thermal activation and 
sodium carbonate uniformly, and melting at high temperature to obtain a molten mixture; secondly, mixing the molten mixture and water under the water solution condition to dissolve out 
sodium silicate, filtering to obtain filter residues and 
drying the filter residues; thirdly, completely stirring the dried filter residues and a 
sodium hydroxide solution under the alkali 
dissolution condition, filtering to obtain a 
silicon aluminum solution, and 
ageing the 
silicon aluminum solution to obtain a precursor; finally, performing hydrothermal 
crystallization treatment on the precursor, and filtering, water-washing and 
drying to obtain the 4A 
zeolite. According to the synthesis method, the gangue serves as the 
raw material, the gangue is subjected to high-end resource-based development and utilization, and the gangue does not need to be subjected to acid leaching pretreatment, so that secondary 
pollution on the environment is reduced; and an aluminum source does not need to be added in the synthesis process, so the method is simple, high in 
operability and low in cost.