The quantitative relationship between the electric charge quantity (Q) and OH^- concentration (c_OH^-) was established by measuring the variation of pH value of simulated concrete pore solutions by impressed current cathodic protection (ICCP), and corrosion products formed on the titanium mesh electrode were quantitatively characterized. The results indicate that by the same polarization time, a lower c_OH^- was related to a higher applied current density; the accumulation of corrosion products on titanium mesh surface was also much heavier. By the same current density, the consumption rate of OH^- was larger in the chloride-containing solution rather than that in the chloride-free counterpart. The relationship between Q and c_OH^- in simulated concrete pore solution by the applied cathodic protection follows logistic regression equation, thus this equation can be used to evaluate the descent of pH near the anode, and further predict the effect of acidification of solutions on the corrosion of external anode by the applied cathodic protection.