The work aims to synthesize Si4+ doped and Zr4+-Si4+ co-doped barium ferrite absorbents through the solid-state method to improve the absorption performance of barium ferrite absorbers in the Ka-band (26.5-40 GHz), reduce the sintering temperature and improve the preparation efficiency. By analyzing the microstructure and phase composition of the absorbents when only Si4+ was doped, an appropriate amount of Si4+ was selected. Subsequently, BaFe11.8−yZrySi0.2O19 was prepared through doping of barium ferrite with Zr4+ and Si4+, and the effects of the Zr4+ doping amount and sintering temperature on product composition, microstructure, and electromagnetic performance were investigated. The study revealed that Si4+ doping effectively reduced the sintering temperature and promoted solid-phase reaction, but excessive doping lead to the formation of secondary phases; therefore, the optimal doping amount of Si4+ was x=0.2. After co-doping with Zr4+ and Si4+, both the grain size and dielectric constant exhibited minor changed with increasing temperature, and the real and imaginary parts of the dielectric were approximately 8.5 and 2.5, respectively. The natural resonance frequency decreased from 35 GHz to 28 GHz as the Zr4+ doping amount increased from y=0.2 to y=0.4, and this change was less affected by temperature. Consequently, Zr4+-Si4+ co-doping can increase the solid solubility of the doping elements at a lower sintering temperature, enabling the effective adjustment of the resonance peak to the Ka band, thereby improving the magnetic loss of the material. Finally, the absorbent BaFe11.4Zr0.4Si0.2O19 sintered at 1 150 °C was filled into the matrix with a mass ratio of 3∶1. When the coating thickness was 0.82 mm, the absorbing materials exhibited a minimum reflection loss (RL) of −29 dB at 39 GHz and below −15 dB across the Ka band.