The (Ca_0.96D_0.04)MnO₃(D=Ca, Sr, Rb, Sm) oxide powders were prepared by sol-gel method firstly, and the CaMnO₃(CMO) bulk samples were prepared thereafter by spark plasma sintering in argon atmosphere and air atmospheric sintering at ordinary pressure respectively. After analyzing their phase compositions, the better preparation method of CaMnO₃ bulk samples are selected and then the (Ca_0.96D_0.04) MnO₃ (D=Sr, Rb, Sm) oxide bulks were prepared. Finally, the phase composition, microstructure and thermoelectric properties of (Ca_0.96D_0.04) MnO₃ (D=Ca, Sr, Rb, Sm) bulk samples are measured and analyzed. The results show that the CaMnO₃(CMO) bulk samples prepared by spark plasma sintering in argon atmosphere have occurred phase decomposition, which is due to the SPS poor oxygen sintering environment. High quality (Ca_0.96D_0.04)MnO₃(D=Ca, Sr, Rb, Sm) bulk samples with single phase can be prepared by atmospheric sintering at ordinary pressure. The dimensionless figure of merit ZT is improved with peak values of 0.11,0.08,0.07 at 873K for (Ca_0.96D_0.04)MnO₃(D= Sr, Rb, Sm) bulk samples respectively, which are about 1.3~2.2 times higher than that of the un-doped samples.