In this work, we elaborately explored relationships between phase structure, dielectric and ferroelectric performances in (Pb, Ba)ZrO3 system to clarify its confusing characteristics. 1) Incorporation of barium decreased phase transition temperature, and orthorhombic–orthorhombic + rhombohedral–pseudocubic phase transition sequence was determined for fresh sample and more complicated transitions for poled ones. 2) Macroscopically, antiferroelectric–ferroelectric + antiferroelectric–ferroelectric relaxor –Debye medium states at room temperature were deduced, evidenced by multi-dimensional analysis. 3) The observed ferroelectric behaviors were substantially originated from synergistic ferroelectric + antiferroelectric domain switching for x = 0.90–0.75 compositions, which were innovatively justified by single-bipolar-cycle measurements. 4) Antiferroelectric + ferroelectric ↔ ferroelectric ↔ relaxor phase boundaries were built in (PbxBa1-x)ZrO3, where polarization and strain value reached to maxima at corresponding x = 0.75 and 0.65 compositions. Finally, phase diagram in (PbxBa1-x)ZrO3 binary system (0.5 ≤ x ≤ 1.0) was constructed and refined, thus provided a guideline for compositional design in this system.