Abstract: The fly ash from the coal-fired power plant was activated by atmospheric pressure and low temperature sub-molten salt method. The silicon and aluminum species with high stability and low chemical activity in fly ash were transformed into amorphous silicon and aluminum with high chemical activity. The activated fly ash was used as raw materials to synthesize aluminosilicate molecular sieve SAPO-11. The content of active silicon and aluminum in activated fly ash was determined by ICP-OES. The phase and morphology of molecular sieve samples were characterized by XRD and SEM. The test results show that the sub-molten salt activation method can better activate the silicon and aluminum species in fly ash to amorphous silicon and aluminum with high chemical activity. The fly ash activated by sub-molten salt can successfully synthesize SAPO-11 molecular sieve. This study can provide a green and efficient activation method for the synthesis of molecular sieves from fly ash, which has certain theoretical value and guiding significance for the high-value resource utilization of coal-based solid waste fly ash.