In the ultrasonic honing processing,design of the transformer composed of horn and processed gear is a key technology,it is very important to explore the new type of transformer. Based on variable cross-section composite horn wave equation of longitudinal vibration and displacement equation of medium thickness circular plate in flexural vibration,the resonance frequency equations of the system are derived according to the non resonant and boundary condition of the ultrasonic gear honing composite transformer composited of composition horn and medium thickness circular ring. The design parameters,the resonance frequency and the amplitude distribution of horn and ring are studied by using numerical calculation method,at the same time,the influence of the transformer geometric parameter on the system resonance frequency is analyzed. The result shows that,the finite element analysis of the resonant frequency and the calculated results are basically consistent with the theoretical calculation result and experimental test,the system resonance frequency decreases with the increase of the length of the composite horn,When the radius ratio of the composition horn two ends and the length of the paragraphs remain unchanged,the system resonance frequency increases with the increase of both ends radius is proportional,it increases with the increase of ring thickness radius ratio when other parameters are constant. The results not only confirmed the correctness of the non resonance theory but also provides a theoretical basis for design and application of ultrasonic gear honing transformer.