In this work, the fly ash-based geopolymer (FAG) were prepared by using fly ash as a source of aluminosilicates and a mixture of sodium hydroxide and sodium silicate as an alkaline activator for studying the effects of sodium silicate to sodium hydroxide and solid to water ratios. A total of nine mixtures were evaluated by considering the effects of ratio of Fly ash/alkaline solution FA/AS (three levels: 1.5; 2.5 and 3.5) and ratio of Sodium silicate/sodium hydroxide SS/SH (three levels 1.5; 2.5 and 3.5) on the compressive strengths of the geopolymer FAG mix at 7 and 28 days. The optimal FAG mixtures were characterized using several analytical methods such as XRD, FTIR and SEM analysis. The fire resistance of geopolymer FAG was evaluated by weight change before and after heat exposure to elevated temperature (600°C, 800°C and 1000°C). The 2.5 of Fly ash/alkaline solution and of Sodium silicate/sodium hydroxide ratios showed the best mechanicals results 30MPa while for fire resistance the four samples of GP6, GP7, GP8 and GP9 with (2.5;3.5), (3.5;1.5),(3.5;2.5) and (3.5;3.5) respectively, (Fly ash/alkaline solution; Sodium silicate/sodium hydroxide ratios); were showed the best results after exposing to 1000°C.