The BaCo2Fe16O27 ferrite particles have been prepared by sol-gel combustion technique. The products have been characterized by TG/SDTA, XRD, SEM and LPSA. The Microwave absorbing composite used in the load side of isolator with BaCo2-xZnxFe16O27 (x=0.0, 0.6, 1.0, 1.4, 2.0) as absorber have been prepared. The thermal degradation temperature of this kind of absorbing materials is 350 °C. When the average density is 2.62 g/cm3, the breakdown voltage is 1.4kV/mm. In the frequency range of 2 GHz-16 GHz, the absorption effects of BaZnxCo2-xFe16O27 (x=0.6, 1.4) are better than that of the single Co2-W or Zn2-W. In the frequency range of 9 GHz-16 GHz, the absorption loss of x=0.6 is better than others, which is in the range of 9.7~15.0 dB.