Abstract: Sr_1-xBi_xTiO₃ ceramics were prepared by conventional solid state reaction.The dielectric properties, defect structure and defect dipoles of SrTiO₃ ceramics doped with Bi were investigated. The crystal structure were characterized by X-ray diffraction(XRD). The results show that the second phase does not occur in doping range. Obtained by the General Utility Lattice Program, the stable defect dipoles are 2Bi_Sr^·+V_Sr"、V_O^··+V_Sr"、2V_O^··+V_Ti''' and V_O^··+2Ti_Ti'.The results suggest that all the dielectric relaxations are related to the thermally activated process by following Arrhenius law.With the content of Bi increasing, the relaxation activation energy of the peaks of dielectric loss increases and the degree of dielectric relaxation decreases.