High-entropy oxides with complex compositions can be designed as novel ferroelectric materials with interesting physical consequences. A single-phase (K0.5Bi0.5)0.2Ba0.2Sr0.2Ca0.2Mg0.2TiO3 high-entropy ceramic with a perovskite structure was synthesized by a conventional high-temperature solid-state method, and the dielectric and ferroelectric properties of the ceramic were investigated. The results show that there are no relaxation peaks in the test temperature range because of the multi-element doping. The dielectric constant of ceramic has a high-temperature stability at < 300 ℃. The maximum dielectric constant of 8 887 is obtained at 100 Hz and 650 ℃. The introduction of high-entropy oxide in the ceramic can have high-entropy ferroelectrics in complex materials, and modify the properties of electronic ceramic.