The invention belongs to the technical field of comprehensive utilization of fly ash, and particularly relates to a novel process for synthesizing a molecular sieve by adding alkali to calcine the fly ash by a wet method. The process comprises the following steps: the fly ash is ground, iron in the fly ash is removed by a high-strength magnet and acid dissolution, the fly ash is filtered and washed to be approximately neutral, then a proper amount of strong base is dissolved in water to be mixed with the fly ash to be dried, the calcination activation is performed at proper temperature, the quenching treatment is performed, a calcinated material and other auxiliary materials are ground into slurry and iron in the materials is removed by the high-strength magnet, and a molecular sieve product can be obtained through gel formation, crystallization synthesis, filtration, washing, and drying at the preset temperature. The adoption of the process can remarkably improve the whiteness, crystallinity degree and yield of the molecular sieve product synthesized by the fly ash by a hydro-thermal method, can also shorten the reaction time of the gel formation and the crystallization synthesis, improve production efficiency, reduce the consumption of acid and alkali raw materials, and reduce the activation calcination temperature of the fly ash and the consumption of thermal energy.