Abstract: At present, the thermoelectric effect of cement-based materials is mainly enhanced by adding a large amount of functional fillers. However, the high content of the functional filler increases the cost, degrades their mechanical properties and hinders their wide application. It is found in this study that the pure cement paste without any functional fillers shows a significant ionic thermoelectric effect due to the freely moving ions in the pore solution of the cement-based materials. The ionic thermoelectric effect of the cement-based materials was studied by comparing the thermoelectric voltage of pure cement paste before and after drying, and the mechanism of the ionic thermoelectric effect of pure cement paste was further explored through ion leaching and saturated alkali solution experiments. Results show that the pure cement paste before dry shows a significant n-type ionic thermoelectric effect due to the thermal diffusion of OH⁻. The decrease of the concentration of OH⁻ in the leaching process leads to the change of ionic thermoelectric voltage from n-type to p-type. After saturated in NaOH solution, the type of cations has a significant effect on the ionic thermoelectric properties even under the condition of high OH⁻ concentration. In addition, the Seebeck coefficient of cement paste without any functional filler can reach 1.133 mV·℃⁻¹, and the power factor P_F can reach 0.042 μW·m⁻¹·℃⁻², which is higher than that of some cement-based composites with 5% functional filler in the literature.