MnO2 nanopowders were chosen as the thermoelectric component to increase the thermoelectric effect of cement composites. The MnO2 nanopowders were synthesized by hydrothermal method and then incorporated into cement composites. The thermoelectric property（generally called Seebeck effect）of this cement composite was explored with different use level of MnO2 nanopowders. Besides, the enhancement mechanism was discussed in detail. The results show that the Seebeck coefficient of the cement composites increases steadily with the added MnO2 nanopowders use level. The maximum Seebeck coefficient was higher than 33000μV/℃ when the MnO2 nanopowders use level was 50%, which was about 30 times higher than that of fiber reinforced cement composites. The research results endow the cement composites with MnO2 a potential application in energy harvesting and air conditioning system in future buildings.