This Study purposed to review on the strength of geopolymer mortar and the change in liquidity depending on the mixing ratio of alkali-activator in developing the geopolymer mortar using bottom ash as binder. Alkali-activator was used through mixing 9M-Sodium hydroxide (SH) and 3 kinds of Sodium sillicate(SS) and its strength was measured by material age after curing for 48 hours at 60°C. As a result, the pressure strength was shown as 40MP when the mass ratios of 9M-Sodium hydroxide and 3 kinds of Sodium sillicate were35 vs. 65 and 50 vs. 50, but the solution of the mass ratio of 50 vs. 50 showed the rapid solid phenomenon in the process of mortar manufacturing, thereby disadvantage in construction. In addition, in case of storing the mixed solution in room temperature, as the mix ratio of 9M-Sodium hydroxide increases, the solution solidified. Accordingly, when considering on strength, liquidity and storage, it’s most preferable to fix the mass ratio of 9M-Sodium hydroxide and 3 kinds of Sodium sillicate at 35 vs. 65.