The multilayer composites were prepared by cofiring Pb(Ni1/3Nb2/3)O3-based ferroelectrics and NiCuZn ferrite using tape casting processes. The interface and grain growth of the composites were investigated. The results show that the sintered interface of composites is solid, continuous with no delamination and cracks, which should be attributed to the chemical compatible of the two materials. The grain growth of ferroelectrics adjacent to the interface is different from that far from the interface. It should attribute to Fe3+ diffused from the ferrite to ferroelectrics and soluted into the perovskite lattice. The difference factor dD is proposed to describe the microstructure difference between the interface and the inner parts.