The microstructure and electrical conductivity of A2Zr2O7 ceramic have been investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED), Raman spectroscopy and Impedance spectroscopy. The results show that the degree of structural order of rare-earth zirconates A2Zr2O7 ceramics gradually decreases with decreasing ionic radius of rare-earth cations. The Sm2Zr2O7 and Eu2Zr2O7 ceramics exhibit an ordered pyrochlore phase, while Gd2Zr2O7 and Dy2Zr2O7 ceramics have a disordered fluorite phase. Pyrochlore-type Eu2Zr2O7 ceramic with a relatively low structural order degree shows the maximum grain conductivity of 1.03?10–2S?cm–1 at 1173K, as compared with that of the other rare-earth zirconates.