The electronic structures of Ca₃Co₂O₆ and Ni-doped ones are calculated using density functional and discrete variation method (DFT-DVM).The relation between electronic structure,chemical bond and thermoelectric property is discussed.The results indicate that the highest valence band (HVB) and the lowest conduction band (LCB)are mainly contributed from Co3d,Ni3d and O2p atomic orbitals.The property of semiconductor is shown from the gap between HVB and LCB.The gap of Ni-doped ones is less than that of Ca₃Co₂O₆.The covalent and ionic bonds of Ni-doped ones are both weaker than those of Ca₃Co₂O₆.The thermoelectric property may be improved from adding Ni element into the system of Ca₃Co₂O₆.