Lead zirconate titanate (PZT)-based piezoelectric ceramics are a type of functional material with a wide range of applications, which can be used in ultrasound transducers, piezomotor, medical ultrasound transducer, and surface acoustic wave filter, etc. Improving the piezoelectric property of PZT-based piezoelectric ceramics through modification has always been a research hotspot in this field. In this work, Sm-0.25PMN-0.75PZT piezoelectric ceramics near the morphotropic phase boundary (MPB) were fabricated by conventional solid-phase reaction method, and its microstructure and macroscopic property were systematically studied. The research results show that introduction of Sm³⁺ can enhance the local structural heterogeneity of piezoelectric ceramics, accelerate the dielectric response, and improve the piezoelectric performance. When Sm³⁺ is excessively introduced, the long- range continuity of ferroelectric polarization is interrupted in a large area while the piezoelectric performance decreases. The performance of the optimal composition piezoelectric ceramic obtained in this experiment is: high voltage electric coefficient (d₃₃~824 pC/N), high voltage electric voltage constant (g₃₃~27.1×10^-3 m²/C), and relatively high Curie temperature (T_C~178 ℃). The electrostrain is less than 5% in the range of room temperature to 150 ℃, with relatively good temperature stability. Therefore, this PET-based relaxor-ferrelectric ceramic is a high- performance piezoelectric material with great application prospects.