Effect of sulfate solution on the geopolymer formed from electric arc furnace slag (EAF) along with water cooled slag and cement kiln dust was studied. Activation was carried up on usage of 25% CKD as it bears high alkali content that can initiate and propagate the polymerization process. The formed geopolymer products were immersed in 5% MgSO4 solution to determine the stability up on sulfate attack. FTIR, XRD, SEM, compressive strength and water absorption were utilized to examine the resulted geopolymer product under sulfate attack. Results showed that, the compressive strength of geopolymer specimens increase with EAF slag up to 50% then decrease with further slag increase, possessing stability up 12 months and giving an increased compressive strength than the control mix that has not EAFS by 6.53%, 14.72%, 47.44% and -4.89 % after immersing ages of 3 months and 2.26, 14.26, 43.97 and 19.98 % after immersing age of 12 months for replacement by 10, 25, 50 and 75% of EAFS, respectively. Data elucidated a good stability and resistance of mix containing slag substitution by 50 % EAF and 25 % GGBFS and results in further enhancement in both mechanical and microstructural characteristics than the non-immersed samples (28days).