The effects of different activators on compressive strength of fly ash-based geopolymers were studied.It is shown that the activative effect of NaOH and KOH solution with different concentration is weak,the compressive strength of fly ash-based geopolymers is low,but the activative effect intensifies when NaOH or KOH solution mixes with K_2SiO_3 solution,and the compressive strength improves too.The K_2SiO_3 solution shows the best activative effect,the compressive strength of fly ash-based geopolymers increases with increasing concentration of K_2SiO_3 solution.When the solution concentration is 2 mol/L,the 28 d compressive strength reaches the maximum,then it decreases with the increase of the solution concentration.It is guessed that geopolymerization is a stoichiometric reaction.