Abstract: The primary and secondary factors of influencing the microstructure of concrete after electrochemical realkalization were investigated by MIP and SEM. The results show that current density has the largest effect, that the secondary influence factors are the electrify time and concentration of solution. When the electrolyte composed of 1 mol/L Na2CO3 solution, electrify time of 14 days and electrical current density of 3 A/m2 were adopted, the best efficiency can be achieved. Experimental measurements of porosity in standard specimens, completely carbonated specimens and realkalization specimens indicate that: realkalization has considerable impact on the pore size distribution and porosity of concrete. After realkalization the total pore volume is decreased, gel pores cover the majority of the total, and the concrete microstructure becomes very compact. It indicated that realkalization could improve the microstructure and durability of concrete.