A complex equivalent circuit model for cement-based piezoelectric ceramic composite in the thickness mode is presented. The losses of the composites have been taken into account by considering the elements of the circuit as complex quantities; one factor causing the losses is the electrical leaking of cement matrix. The simulated curves derived from the complex circuit model match the experimental results closely. The calculation of the equivalent circuit parameters from the material properties is straightforward. Conversely, the material constants of composites can be derived when the complex circuit parameters are known. A reciprocal relationship exists between the material constants and equivalent circuit parameters have been proved in this study both in theoretically and experimentally. © 2008 Elsevier Ltd. All rights reserved.