Ca-substituted magnetic-dielectric composites were prepared by the conventional solid-state method. XRD and SEM techniques are employed to investigate the phase composition and microstructure of ferrite particles. The complex permeability, capacity and impedance were measured with HP4291B and 4572A instruments, respectively, in the frequency rage from 1MHz to 1.8GHz. The results showed that a improvement of resistivity and Q factor occurs with the increasing content of CaCO3. The average grain size and dielectric loss decrease with increasing Ca-additions. It also found CaCO3 can promote the sintering process.