The growth of PZT single crystals is an area of special interest because single crystals with specific orientations possess better piezoelectric properties than ceramics. However, the growth of PZT single crystals is limited by their high melting point and incongruent melting behavior. In this work, large-size PZT-5H single crystals are grown using the solid-state crystal growth (SSCG) method with excess PbO addition. An ultra-high piezoelectric performance (d₃₃ ∼ 1800 pC N⁻¹, ∼ 2400 pm V⁻¹ at 3 kV cm⁻¹ and k₃₃ ∼ 87%) was achieved in the [110]-oriented PZT-5H single crystals with 4 wt% excess PbO addition in the growth process. The variation of piezoelectric coefficients is explained by the ferroelectric phase coexistence adjusted by the excess PbO induced chemical composition fluctuation in the PZT-5H single crystals, which results in flattening of the free energy profile and improved piezoelectric performance. With the increase of the PbO liquid phase, the composition of PZT-5H single crystals shifts to promote the monoclinic and rhombohedral phases. This research paves the way for designing high-performance piezoelectric materials by manipulating the ferroelectric phase coexistence with SSCG.