Low-temperature sintering of 0.25PMN0.40PT0.35PZ ceramics was investigated using CuO as a sintering aid. Effect of CuO on the sinterability, microstructure, and electric properties of 0.25PMN0.40PT0.35PZ system was systematically studied. The CuO addition significantly reduced the sintering temperature of 0.25PMN0.40PT0.35PZ from 1260 degrees C to 950 degrees C. SEM results indicated that a dense microstructure without any second phase was obtained when the amount of CuO was 0.25 wt%, which gave rise to high values of d33 = 532 pC/N and kp = 58.4%. A large field-induced longitudinal strain 2.28% (at 30 kV/cm) can also be obtained for 0.25 wt% CuO-added specimens, which shows a great promise for multilayer actuator applications.