xBST-(1-x)YIG composite ceramics with x=0~1 were prepared by solid-state reaction method. The variations for phase compositions were determined by XRD, and the magnetic and dielectric properties of the composites were studied in the frequency range of 100Hz~1GHz. The results showed that the composites (x=0.1~0.9) are consisted of BST phase and YIG phase and no significant chemical interaction occurs between these two phases. The composite materials exhibit excellent frequency dependences of dielectric and magnetic properties. The resonance frequency and high frequency characteristics of YIG are improved by additions of BST, and when x=0.3, xBST-(1-x)YIG has the best dielectric and magnetic properties.