The influence of compound adding Bi2O3-Al2O3 to the NiZn ferrite on the mechanical strength and heat shock performance was investigated in this paper. The micro structure and electromagnetic properties of NiZn ferrite were represented and analyzed by using XRD and SEM. The experimental results indicate that adding 0.6%Bi2O3+1.2%Al2O3 can obviously improve the microstructure of NiZn ferrite and electromagnetic properties. The mechanical strength reaches to 150 MPa. The availability of NiZn ferrite is up to 95% after the thermal shock Meanwhile it has good electromagnetic properties.