Abstract: The structure and dielectric properties of (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇-based ceramics with Bi³⁺ substituted by La³⁺ were investigated.(Bi_1.5-xLa_xZn_0.5)(Zn_0.5Nb_1.5)O₇samples were prepared by conventional method.The X-ray diffraction and SEM were used to analyze the microstructure.The La-doped samples held primarily pyrochlore single-phase on the whole field, and its stable range was determined by the tolerance factor (R_A/R_B values).With the increase of amount of La³⁺ substitution, crystal cell parameters showed a trend from ascent to descent.The dielectric properties varied with the microstructure.The dielectric properties of BLZNT-x samples exhibited as:ε=130~170,tanδ=0.35-0.9×10^-3at 1 MHz,and the frequency characteristics at high end (＞100kHz) were optimized through the La-doping.