Bi doped Ca3Co4O9 thermoelectric materials were prepared by solid state reaction. The phase and morphology of the samples were investigated by XRD and SEM. The conductivity of Bi doped Ca3Co4O9 ceramics were investigated with four-wire conductivity measurement. The results showed that all the Ca3-xBixCo4O9 samples were single phase of Ca3Co4O9. The grains were in lamellar structure observed by SEM. With Bi doping content increase, average grain size and the relative density can be increased greatly and the conductivity can also be improved, which are related to the relative density, the growth with preferred orientation and average grain sizes.