A material with stable permittivity (the capacitance is within ±15% of room temperature capacitance) at an ultra-broad temperature range of −55–300°C has been achieved by doping appropriate amount (mol%) of Pr6O11 in multicomponent BaTiO3–(Bi0.5Na0.5)TiO3–Nb2O5 based ceramics. A remarkable high ceiling working temperature of 300°C has been achieved by the doping of Pr6O11. It played a crucial role in the stability of high-temperature dielectric properties. While increasing the doping content of Pr6O11, the dielectric constant was decreased significantly at the temperature range of 200–300°C and the maximum TCC value was reduced from 39% to only 4%. XRD results showed the substitution of Pr ion appeared in both Ba-site and Ti-site. The substitution decreased the spontaneous polarization of BaTiO3 and then weakened the ferroelectricity of BaTiO3. As a result, the temperature stability of samples was improved obviously. Besides, Pr6O11 addition promoted the formation of sheet grains, which were consisting of BaTi4O9. The best dielectric and electrical properties (εr=1608, tanδ=1.54%, ρV=2.15×1012Ωcm) at room temperature appear in the sample with 0.6mol% Pr6O11 addition.