To reduce the degree of efflorescence in the alkali activation metakaolin geopolymer, modified 5A zeolite with cation exchange property was used to reduce the content of free alkali metal cations in the pores of geopolymer. The effect of modified 5A zeolite on the microstructure and properties of geopolymer were investigated by compressive strength test, pore structure analysis (BET) and SEM-EDS. The cation content in the leachate was detected by inductively coupled plasma optical emission spectrometer (ICP-OES), and the efflorescence area of geopolymer was calculated by Image Pro Plus software in the fixed efflorescence mode to evaluate the effect of modified 5A zeolite on the efflorescence degree of the geopolymer and reveal the effect of modified 5A zeolite on the migration patterns of Na+ and Ca2+ in geopolymer. The results show that the modified 5A zeolite with 4% (mass fraction) content can optimize the pore structure, enhance the mechanical properties of geopolymer through internal curing and micro-aggregate effect, and exchange cation in pore solution to form (N,C)-A-S-H gel. Na+ leaching concentration reduces by 19.4% and the efflorescence area of geopolymer reduces by 57.3%.