This experiment is to present the development of a new mix design method for fly ash based geopolymer mortars activated using combined sodium silicate and sodium hydroxide solution .it was that the actual compressive strength and actual workability values obtained from test were satisfactory comparable to the designed values. The proposed method concept can be applied to generate relevant mix design charts for various types of geopolymer binders. The production of FA/GGBFS based geopolymer mortar was studied by using 8M and 16M concentration of sodium hydroxide (NaOH), sodium silicate (Na2SiO3)and by 0%, 5%, 10%, 15%, 20% partial replacement of fly ash by GGBFS to study the compressive strength of geopolymer mortar at 7,14 and 28 days of maturity.