A new method of refining the pore structures of cement mortar and concrete by electro migration reaction of silicate ion with Ca(OH)2 in the pore solution to produce C S H gel was proposed. The effects of applied voltage, silicate concentration, duration and temperature on the surface morphology, resistivity, flexural strength and compressive strength of prepared mortar samples were investigated. It is found that the overlay formed on the sample surfaces are enhanced, and the resistivity, flexural strength and compressive strength are initially increased and then decreased with the increase of applied voltage and duration. Besides, the amount of formed overlay, resistivity, flexural strength and compressive strength are all lowered with the increase of silicate concentration and applied temperature. From this experiment, it is found that the best effect on the resistivity and strength is observed at the voltage of 48V, the silicate concentration of 005mol/L, the duration of 21d and the temperature of 20℃. Moreover, the mechanism for the proposed method was studied by scanning electron microscopy(SEM）and X ray diffractometer(XRD).