SnO 2-Zn 2 SnO 4 composite ceramics have been prepared using the traditional ceramic process and the relations between the current density and applied voltage have been investigated. The results show that with the increase of Zn 2 SnO 4 content, the breakdown voltage of the SnO 2-Zn 2 SnO 4 composite ceramics reached a minimum and simultaneously, the semi-conductive degree achieved the maximum at x = 0.13. With the increase of Zn 2 SnO 4 content, the barrier height changed slightly and the value for each sample was about 0.8 eV at room temperature, whereas, the barrier height increased obviously with increasing testing temperature. In the imaginary part of electric modulus spectrum, a peak was presented and with the increase of temperature, this peak shifted to high frequency. From the shifting of modulus peak, the activation energy about 0.38 eV was obtained according to the Arrhenius law. The results suggest that the Schottky barrier at the grain boundary plays a key role in the origin of the nonlinear property for SnO2-Zn2SnO4 composite ceramics and the oxygen vacancies are important to the barrier formation.