A composite varistor was fabricated using Ni powder as conductive filler and PNZST antiferroelectric powder as electrostriction matrix. The composite is an electrical insulating material when an electrical field is not applied. When the electrical field was applied to the composite, the PNZST powder matrix was distorted. A conduction path was formed in the composite because of the distortion of the electrostriction matrix and thus the composite became a conductive material when the electrical field was applied. Composites using an Ni filler with 4-mu m particle size and a PNZST matrix with 2-mu m particle size showed a varistor property with volume fractions 33% and 37%; the nonlinearity coefficients of the composites were 3.85 and 3.82. The composites using an Ni filler with 40-mu m particle size and a PNZST matrix with 2-mu m particle size also showed varistor properties with volume fractions 50% and 53%, and nonlinearity coefficients of the composites were 3.65 and 3.12.