Lead zirconate titanate (PZT) ceramics with one-dimensional ordered pore channel structure (3-1 type porous PZT ceramics) were prepared by a freeze-casting process. Interestingly they showed higher piezoelectric coefficients than those of porous PZT ceramics of other connectivity patterns and even corresponding dense ceramics. The presence of unidirectional porosity, formed by sublimation of directional freezing solvent, markedly affects the microstructure, including grain orientation and domain configuration. XRD patterns of different sections indicated the presence of partially preferred grain growth. Grains along the through-pore channel direction (crystal growth direction of frozen solvent) were preferentially [002]-oriented. The porosity caused the reduction of domain size in unpolarized porous ceramics, and then the rise of the polarization rotation in poled ones. Both the oriented grain growth and small domain size enhanced the piezoelectric responses of 3-1 type porous PZT ceramics. From the structural description, including grain orientation and domain configuration, this work provides two direct evidences for the origin of the ultrahigh piezoelectric properties in 3-1 type porous PZT ceramics.