Abstract: The radial vibration of a radial composite round tube piezoelectric ultrasonic transducer was studied. The transducer consists of an inner radially polarized short piezoelectric ceramic round tube and an outer short thinwalled metal prestressed tubular shell which are compounded in the radial direction. Based on the elastic dynamics theory and the electromechanical analogy, the equivalent circuit of the radial composite piezoelectric transducer is derived. The analysis formulae of the resonance frequency and the antiresonance frequency equation as well as the effective electromechanical couple coefficient of the transducer are obtained. By testing the radial resonance frequencies and the effective electromechanical couple coefficients of some trialmade transducers,it is shown that the theoretical radial resonance frequencies of the transducers from the frequency equation in this paper are in a good agreement with the measured results.