The present invention relates to a process for synthesis of flyash based Zeolite-A, said process comprising grinding and mixing of flyash and caustic soda in a ratio of 1:1.2 and optionally adding sodium aluminate or aluminium hydroxide to obtain a fine homogeneous fusion mixture; heating the said mixture in an inert vessel at about 500-600.degree. C. for about 1-2 hrs. to obtain a fused mass; cooling, milling, and mixing the said fused mass in distilled water for about 8-10 hrs. with simultaneous optional additon of sodium aluminate or alum solution, in the present or absence of NaC1 followed by optional addition of zeolite-A seeding to obtain amorphous alumino -silicate slurry; subjecting the said slurry to hydrothermal crystallisation at about 90-110.degree. C. for 2 to 4 hrs. to obtain Zeolite-A crystals; and washing the said crystals with water and then subjecting the washed crystals to oven drying at about 50-60.degree. C. to obtain the FAZ-A crystals.