Abstract: The poor temperature stability of the K_0.5Na_0.5NbO₃ ceramic has always been the main problem limiting their application. Existing methods often reduce the dielectric constant while improving temperature stability. In this work, a multi-scale control strategy of Ta₂O₅/La₂O₃ co-doping is proposed for achieving synchronous improvement of temperature stability and dielectric constant of K_0.5Na_0.5NbO₃ based ceramics. In particular, the 0.96K_0.5Na_0.5Nb_0.7Ta_0.3O₃·0.04La₂O₃ ceramic sample exhibited excellent properties: Dielectric constant at room temperature (ε_{100 kHz})=1580, dielectric loss (tanδ)=0.05, temperature stability with the variation of dielectric constant (Δε_r)≤15% over a wide temperature range 20—230℃, and a diffusivity parameter γ of 1.96, which is close to that of an ideal relaxor ferroelectric, while remanent polarization decreased and brokendown field strength (E_b) increased to 5 μC/cm² and 80 kV/cm, respectively. The oxygen vacancy polarization and ion vacancy polarization generated by defect dipoles formed by Ta₂O₅/La₂O₃ co-doping increase the dielectric constant. The strong oxygen bonding ability of La³⁺ and the ideal relaxor ferroelectric formed by co-doping further enhance temperature stability. This study breaks the limitations of single polarization and has certain guiding significance for further expanding the application of K_0.5Na_0.5NbO₃ in multilayer ceramics capaitor (MLCC).