The effect of temperature on the resistivity of Sn-Pb alloy-loaded PS composites was studied. The composites have distinctive positive temperature coefficient (PTC) effects with high PTC intensity, abrupt PTC transition, etc. According to SEM and EDAX analyses, the morphology of the alloy particles in the composites remained unchanged as the temperature reached the melting point of the alloy, while the alloy dispersion changed. The viscosity of the composites decreased sharply when the alloy melted.