Abstract: The energy band structures of Bi-Sr-Ca-Cu-O superconductors were calculated by performing the tight-binding calculation method on the basis of EHT approximation. Results show that the Fermi surfaces are closed on the a^*b^* planes. The increase of electronic state densities on the Fermi level is consistent with the rise of T_c in this system. The regular changes of the net charges of Cu and O indicate that the ionio States of Cu and O in the Cu-O plane may influence the superconductivity of this system.

Key words: band structure, Bi-Sr-Ca-Cu-O, superconductor