Abstract: Three laminated plate transducer is studied under three different boundary conditions and the expressions of the resonant frequency and the effective electromechanical coupling coefficient are derived by using Rayleigh method. Transducer resonant frequency and effective electromechanical coupling coefficient are analyzed and compared with the variation of the structure parameters of the transducer by means of numerical calculation, and the calculated results are compared with the results of finite element simulation. The results show that the effects of structural parameters under different boundary conditions of the transducer on the resonance frequency and the effective electromechanical coupling coefficient are different:for fixed structural parameters of the transducer, the resonant frequency is the greatest in free boundary condition, the next in fixed boundary condition and the minimum in simply supported boundary condition; the effective electromechanical coupling coefficient varies with the thickness of sheet metal and the thickness and radius of ceramic piece, and each has a maximum value; when other parameters are certain, the effective electromechanical coupling coefficient is the greatest in simply supported boundary condition, and the coefficient value in the free boundary condition is slightly larger than that in the fixed boundary condition. The above-mentioned results provide a theoretical support for the design and application of three laminated bending vibration transducer.