The effect of La2O3 substitutions on structure and dielectric properties of Bi2O3-ZnO-Nb2O5-based ceramics was investigated. Bi1.52xLaxZn0.5 (Zn0.5Nb1.5) O7 samples were prepared by conventional ceramic processing technology. The crystal structure of the Bi1.5Zn0.5 (Zn0.5Nb1.5) O7 sample was characterized as a pure cubic pyrochlore. With a lower amount of La2O3 substitution, the crystal structures were still cubic pyrochlore. Superlattice x-ray diffraction line was identified for some compositions. With the increasing amount of La2O3 substitution, the crystal structure gradually transformed from pure cubic pyrochlore to LaNbO4 phase. The dielectric properties regularly changed with the structure change. The structure-properties relations of the ceramics are discussed.