Abstract: A kind of radial composite ultrasonic transducer with a conical section was studied.The transducer is composed of a metal ring with equal section,an axially polarized piezoelectric ceramic ring and a metal ring with conical section and the radial dimension of the transducer is much larger than the height.The metal ring with conical section satisfies the equation h=h₀r,and h₀ is a constant.Based on the plane stress radial vibration theory,the electromechanical equivalent circuit of the transducer was derived,the resonance frequency equation and anti-resonance frequency equation were obtained and then the vibration characteristics of the transducer were studied.The firstorder,second-order radial resonance frequencies and anti-resonance frequencies calculated by theory were compared with the numerical simulation results,and the results were consistent.The studies show that the first-order,second-order radial resonance frequencies and anti-resonance frequencies,and effective electromechanical coupling coefficients of the transducer with a conical section are not only related to the material and radial geometry of each part of the transducer,but also to h₀.The greater h₀,the greater the first-order radial resonance frequencies and anti-resonance frequencies,and the effective electromechanical coupling coefficient increases first and then decreases.Compared with the constant section,the conical section transducer radiates sound waves radially outward,with a larger radiation area,higher radiated sound power,and better directivity.