Improving the operating characteristics of electronic devices in high temperature environments urgently requires the development of piezoceramics with both high piezoelectric properties and excellent temperature stability. To overcome the intrinsic trade-off between high piezoelectric property and excellent thermal stability in BiScO₃-PbTiO₃ (BS-PT)-based ceramics, herein, we introduced heterovalent ions (Ca²⁺, Bi³⁺, Nb⁵⁺) of different radii into the A/B sites of 0.37BS-0.63 PT composition, achieving a significantly enhanced piezoelectric coefficient (d₃₃ ~ 568 pC/N) and good thermal stability (Δd₃₃ less than 15% over an ultra-broad temperature range of 20–340 ℃). The simultaneously improved piezoelectricity and temperature stability can be attributed to the slight non-ergodic relaxation induced by weak random fields, the coexistence of long-range polarized order and the continuous rotation of local multiphase polarization vectors, as well as the suppression of oxygen vacancy defects. This work, from the perspective of the combination of structure and function, reveals the synergistic effect of complex heterovalent ions on the optimization of electrical properties, providing a new modification approach for regulating the comprehensive performance of high-temperature piezoelectric ceramics in the future.