The relationship between composition and the electric mechanical properties for La2O3-doped lead niobium stibium zirconate titanate(La2O3-doped PNSZT) piezoelectric ceramics,in which there are tetragonal and rhombohedral coexistent phases, was studied. A series of piezoelectric ceramics with good properties was obtained, having dielectric constants(ε=1500～2500), plane electromechanical coupling factor(Kp=0.45～0.65), mechanical quality factor(Qm=500～1600). These materials are used for making ultrasonic sensor and filter, and marine acoustic launching and receiving device, and so on. It has been explored that the influence of composition on the lattice constant and phase composition of La2O3-doped PNSZT piezoelectric ceramics by XRD(X-ray diffraction). The character of dielectric constant changing of La2O3-doped PNSZT piezoelectric ceramics before polarization and after polarization was studied. The affecting mechanism about composition on the electric machine properties of phase coexistent La2O3-doped PNSZT piezoelectric ceramics was analyzed and discussed.