Microstructural evolving sequence of relaxor ferroelectric Ba6Zr2Nb8O30 (BZN) ceramics has been investigated and discussed. Porous BZN, which has an irregular grain network with pores, can be obtained within a narrow sintering window (sintering temperature of ~1250°C and dwelling time of ~5 h in our experiments). X-ray diffraction-based structure refinements determine the atomic positions and confirm that the porous ceramics has tetragonal tungsten bronze structure with P4bm space group symmetry. It is found that the most porous ceramic has the lowest dielectric constant, highest electric field breakdown strength, and nearly zero macroscopic electric field-induced strain. These features can be related to the porous microstructures by comparing with the denser counterparts and can be well understood by using brick-wall model. Our results may provide useful information for the understanding of microstructure evolving sequence of BZN during sintering and the structural effects on electric properties of ceramics. Our work may also provide a reliable way for developing porous ferroelectric ceramics with special properties.