Piezoelectric Pb(Sb1/2Nb1/2)O3-Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 (PSN-PMN-PZT) quaternary ceramics with the various contents of Pb(Mn1/3Nb2/3)O3 from 4 to 10mol% were prepared. The phase structure of the system was delineated by X-ray diffraction analysis. The surface morphology was examined by SEM. The piezoelectric and dielectric properties were also measured. X-ray diffraction patterns showed that the PSN-PMN-PZT piezoelectric ceramics was composed of tetragonal phase with perovskite-type structure. Study on the influence of Pb(Mn1/3Nb2/3)O3 additives on dielectric and piezoelectric properties indicated that the PSN-PMN-PZT quaternary system exhibited a high mechanical quality factor and well-situated piezoelectric properties. The optimized results of d33 =332pC/N, d31= -105pC/N, Kp=0.58, K31=0.34 and Qm=1658 can be obtained at 6 mol% Pb(Mn1/3Nb2/3)O3. The obtained electrical properties make this composition a good candidate for underwater acoustic devices.