An investigation of the cofired behavior between silver/palladium electrode paste and lead-based relaxor ferroelectric ceramics demonstrated that mismatched sintering shrinkage was caused by differential sintering kinetics. Improvement of the cofired characteristics was obtained by adding different ceramic powders into the electrode paste. The sintering kinetics analyses show that the roles of ceramic additives lie in changing the densification mechanism of the silver/palladium electrode paste. Scanning electron microscopy observations indicate that ceramic additives apparently improve the interfacial bonding by the formation of chemical reaction layers. Compared to BaTiO3-based ceramic additives, which are caused by palladium-lead-based reactions analyzed from the X-ray diffraction spectrum, lead-based perovskite additives will degrade the electronic properties and decrease the melting point of the silver/palladium electrode to a certain extent. Criteria for choosing ceramic additives have been proposed in this paper.