Calcium manganese oxide (CaMnO3) polycrystalline was synthesized by solid state reaction (SSR) and hot-press (HP) methods. The powder of CaCO3 and MnO2 were mixed by ball milling then calcined at 850°C for 10 h and hotpressing at 850 °C for 1 h to obtain the CaMnO3 samples. The crystallography of the samples was analyzed by the X-ray diffraction (XRD). The microstructures of the samples were observed by scanning electron microscope (SEM). It was found that, the sintering process influence the crystalline perfection and have a direct impact on the mechanical properties of CaMnO3 and their aging behavior. The values of the effective elastic modulus was 6 GPa and Flexural strength was 0.417 MPa of CaMnO3 were found to be in the range of corresponding values for high performance and possibility fabricated n-type thermoelectric leg.