In order to effectively complete the performance test of ultrasonic partial discharge detection devices, the technique and launcher of ultrasonic broadband emission were studied. The field axial pressure distribution, the acoustic axis section acoustic pressure distribution, acoustic field directivity characteristics, complex frequency spectrum focal area and other acoustic field characteristics of single frequency and multi frequency ultrasonic transducer sound were analyzed by using MATLAB simulation，and accordingly a complex frequency ultrasonic broadband emission device was designed. Results showed that two columns of the sound wave produced the complex frequency ultrasonic transducer could occur acoustic scattering effect, and the objective of ultrasonic field spectrum width was achieved.