<p>Flash sintering has revolutionized the field of advanced ceramic preparation with the low heating temperature and extremely short sintering time. The difference of doped ions radius can influence the defect structure and resistivity of the sample through lattice distortion, subsequently altering the parameters and dielectric properties of flash sintering samples. By flash sintering technology, co-doped TiO₂ ceramics with the acceptor ions (Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺) and donor ions (Nb⁵⁺) were successfully prepared at 1100&#xa0;°C for 24&#xa0;min. According to the blackbody radiation model, Mg²⁺ and Nb⁵⁺ co-doped TiO₂ ceramics exhibit the highest surface temperature at the moment of flash sintering, approximately 1852&#xa0;°C. Additionally, the co-doped TiO₂ ceramics with Ba²⁺ and Nb⁵⁺ ions exhibit the strongest polarization effect, with a dielectric constant above 10⁵. The acceptor ions with larger ions increase oxygen vacancies by enhancing the stability of defect complexes. The excellent giant dielectric properties are attributed to the combined action of the electron-pinned defect dipole effect and the internal barrier layer capacitor effect.</p>