In order to obtain excellent electrical properties and its temperature stability of KNN‐based ceramics to meet the practical applications, a new lead‐free material system of (1−x)K0.5Na0.5Nb0.96Sb0.04O3‐xBi0.5Na0.5Zr0.8Sn0.2O3 (KNNS‐xBNZS, 0 ≤ x ≤ 0.060) was designed, and the enhanced electrical properties (eg, d33 ~ 465 pC/N, εr ~ 3318, Suni ~ 0.133%) is obtained in the ceramics with x = 0.04. The physical origin of enhanced electric properties should be ascribed to the phase instability of R‐T, resulting in a low‐energy barrier, which can greatly facilitate the polarization switching. Moreover, the temperature stable of piezoelectric constant (d33 or d33*) is measured by three distinctive methods in different phase boundaries (O, O‐T, R‐T) at the temperature range 20°C‐180°C, revealing that the O‐T phase boundary has a relatively good temperature stability. A mode is used to show how to effectively modified the piezoelectric constant (d33 or d33*) and its temperature stability, we believe that such a strategy may further improve the temperature stability of d33 or d33* value in KNN‐based ceramics.