In order to improve the durability of mortar, the method of electro-migration reaction of silicate ion was used to treat mortar. Through comparison tests, the durabilities of different mortar specimens, including a control mortar specimen, a treated mortar specimen without surface coating, and a treated mortar specimen with surface coating, in resisting carbonization, sulfate attack, chloride diffusion, and corrosion of rebar by chloride ions were investigated. The microcosmic mechanism of the effects of this method on the durabilities of mortar was analyzed using a scanning electron microscope (SEM) and a mercury intrusion porosimeter (MIP). The results indicate that the durabilities of the mortar specimens in resisting carbonization, sulfate attack, chloride diffusion, and corrosion of rebar by chloride ions can be sequenced from low to high in the following order: control specimen, treated specimen without coating, and treated specimen with coating. The effect of the method of electro-migration reaction of silicate ion in improving the durability is due to its contribution in production of surface coating and mortar densification. Compared with densification of mortar, the produced coating has a relatively smaller effect on the improvement of durability due to its low thickness and numerous micron-grade pores.