Abstract: As the aluminum and silicon existed in the form of kaolin in the coal gangue，their activities are very low.If the coal gangue is sintered with sodium carbonate at a certain temperature，alumina and silicon dioxide in the coal gangue can be converted into soluble sodium silicoaluminate.The factors that can affect product′s performance were determined by experiments in the synthesis of 4A molecular sieve.Results show that when the mass ratio of sodium carbonate to coal gangue was 1.2，the activation temperature was 800 ℃，the activation time was 1.5 h，the amount-of-substance ratio of Na₂O to SiO₂ was 1.8，the amount-of-substance ratio of H₂O to Na₂O is 42，crystallization temperature was 90 ℃，and crystallization time was 3 h，the calcium exchange ability of the obtained 4A molecular sieve was 305 mg/g and its removal rate to chromium ion in the wastewater reached 83.6%.

Key words: coal gangue, 4A molecular sieve, activation, crystallization