Abstract: In order to study the influence of structural parameters of longitudinal vibration ultrasonic transducer on the viscoelastic heat generation of polymers during the ultrasonic plasticization process, the composition of ultrasonic viscoelastic heat generation system was determined, and then the structure of longitudinal vibration ultrasonic transducer was designed. The ultrasonic viscoelastic heat generation process and the corresponding mechanisms were analyzed. A single variable method was adopted to investigate the influence of structural parameters of the transducer on the longitudinal vibration frequency and maximum amplitude of the particle at the front end of tool head. Finally, the longitudinal vibration excitation of the transducer was loaded on the molten polymers to study the effect of structural parameters on the ultrasonic viscoelastic heating process of the polymer and the time required for reaching its glass transition temperature. The results indicated that the polymer temperature increases nonlinearly with an increase of longitudinal vibration excitation time. The amplification ratio generated the much greater influence on the variation of polymer temperature than on the front cover thickness and tool head length, but there was the least influence on the horn length.